How To Unclog A Shower Drain: DIY Tips & Contractor Quotes

We discuss how to unclog a shower a drain by including useful DIY tips as well as the cost of hiring a professional. Free contractor quotes included.

Let’s just imagine for a moment. You are in the shower cubicle enjoying your morning shower, when you hear shouts from downstairs. Turning off the water you look down and see the tray overflowing onto the bathroom floor. Water is disappearing between the floorboards and reappearing in the downstairs room having soaked through the ceiling. Why is the tray overflowing? The reason is that no one has cleaned the drain for a few weeks. The drain trap has become blocked with a congealed mass of soap, hair, grease, dead skin cells and dirt. All it needed would have been a ten minute job every two weeks and you wouldn’t have the expensive job you have now.

Although we are talking specifically about how to unclog a shower tray today, the methods mentioned will work just as well in any other drain, whether it is a sink, bathtub, toilet or whatever. So don’t be blinkered into thinking these methods won’t work elsewhere.

Today we are going to talk about:

  • What happens when the shower drain becomes blocked?
  • What causes the blockage?
  • How can we clear the blockage?
  • DIY methods to keep the drain clean.
  • What every home should have ready in case of a blocked drain.
  • How much will the DIY materials cost to buy?
  • When to call in a contractor and which contractor to call.
  • How much will the contractor cost to do the job?
  • How not to have the blockage in the first place.
  • How to protect ourselves from harm.
  • What causes a blocked shower drain in the first place?

If you stop to consider what things are washed down a drain when you shower, it isn’t any wonder that the drain becomes blocked.

Hair. The main thing that causes a blockage is hair. When you shower you wash your body and your hair. Humans are mammals and all mammals have hair on their bodies. Extreme agitation and scalp massage can loosen the hair at the roots. The lost hair is washed down the drain and sometimes becomes lodged onto protrusions within the drain. It is a fact that long hair causes more blocked drains than short hair so if you have members of your family with long hair then you must be prepared for some blockages.

Soap. When showering we use soap of some kind, whether it is shampoo, shower gel or hard soap, it all ends up down the drain. If there is already a clump of hair lodged in the drain then the soap scum collects in the hair matrix.

Skin cells. Other things we wash down the drain when we shower are dead skin cells. Dead skin combined with soap clogs in the hair matrix and produces a very unpleasant mess.

Dirt. We wash dirt from our bodies every time we shower. This dirt joins the terrible mess within the drain and contributes to the blockage.
What is a shower drain and how does it differ from other domestic drains?

In the bottom of any domestic water appliance is a drain. Whether it is a sink, handwash basin, toilet, bathtub, washing machine, dishwasher or shower, you are pouring water into a receptacle and you need some way to get the water out. A hole at the bottom will do the job. A shower is unlike all the others in that you don’t want the water to accumulate in the tray. You want the water to exit as fast as you are pouring it in. Normally this works well, the drain hole is big enough to allow all the water to drain away while you shower. Sometimes however the water takes a bit longer to drain and you know something is wrong, but “hey what the heck I haven’t got time to sort it out now, I will fix it at the weekend.”

Unknown to you the combined hair from you and your family has become caught on the cross bar in the drain hole. Long hair is the worst offender for this as it becomes caught easier and is most difficult to remove. Over time the mat of hair filters the soap, grease and other solids which add to the mess in the drain. Eventually the whole drain becomes blocked, just because you didn’t clear it when you first noticed the problem.

Every other drain in your house is accessible from the underneath, but not the shower drain. Usually the shower drain is at most no more than 4” above the finished floor level and usually is flush with the floor. This means that the only way to dismantle a shower drain is from the top.

How to dismantle, unblock and reassemble a shower drain

The designer of the drain and the shower tray is fully aware that the drains become clogged and will have designed a way for you to unblock the drain without having a major demolition job, removing the shower tray and half the floor as well. Anyway, let us run through the method of removing the drain cover step by step:

Sure enough if you look into the drain cover you will see a stainless steel screw (it is actually a bolt but we don’t know that yet). You may see more than one screw, but that doesn’t matter just take out all the screws. The screw head will either need a slot or crosshead screwdriver depending on the type of screw present. Whichever type of screwdriver is required make sure that the blade is the correct size for the screw head.

Insert the screwdriver into the screw head and turn counter-clockwise. The screw will start to move and seem to raise itself into the air as you turn it.
When the screw is almost at the end of its thread (the thread is the spiral groove which runs along the screw shaft) remove the screwdriver.

Using your finger and thumb continue to turn the screw counter-clockwise until you can lift the screw away from the drain. Don’t drop the screw down the drain or it will be lost forever!

Remove the screw and place it safely on the floor away from any holes or cracks where it might fall through. You will need this later.

Using either a straight bladed screwdriver or a pair of long nosed pliers lift the drain cover away from the drain and place it safely next to the screw you have already removed.

At this stage you will have noticed that your knees are hurting and you want a break. Have a look at the ‘screw’ you have just removed from the drain cover and you will notice that the shaft (or shank) is not tapered but parallel. This means that it is not a screw but a bolt. This means that you have just removed it from a threaded hole or a ‘nut’. Look inside the drain and you will see a metal or plastic bar reaching across the diameter of the drain. In the mid-point is the threaded hole where the bolt goes.

Let us move on.

Look down in the drain; you might need a flashlight for this because it is pretty dark and dreadful down there. The most likely places for any blockages are where the hair tangles on the cross bar and then disappears down into the ‘U Bend’ where the rest of the mess has congregated. So … do we remove that lot?

First thing to do is to realise that this part can become a little bit yucky so it might be a good idea to wear some rubber gloves. I hope you have a strong stomach.

Using a sharp craft knife, cut the hair where it is tangled around the cross bar. You will need to cut away all the strands of hair so that it is no longer tangled around the bar. Have a look elsewhere in the drain and if the hair is tangled somewhere else, then cut this as well.

Find a wire coat hanger and straighten it out. Bend one end so that you have formed a small hook. If you haven’t a wire coat hanger then a crochet hook or any piece of stiff wire will do.

Poke the hook into the bend and turn it slightly.

Remove the wire hook and you will bring with it a clump of tangled, greasy, soapy hair.

Pull the tangle from the hook and drop the clump of hair into the toilet if it is nearby. If not then keep it safe and dispose of it sensibly elsewhere. Note: do not wash the hair down the sink, bathtub or hand-washbasin otherwise it will contribute to another blockage somewhere else!

Repeat the fishing action to try to remove as much hair and other muck as you can. You may need to repeat this more than once.
Continue until the hook comes out clean.

Turn on the shower so the water is as hot as possible and rinse the drain with the running water. Hopefully the blockage has now gone and the water runs away as it should.

Now that we have removed the blockage we can re-assemble the drain.

Look into the threaded hole situated in the crossbar and check there is nothing lodged in the hole which might stop the bolt from entering.

Retrieve the drain cover from the safe place and insert it back in the hole.

Make sure the hole in the drain cover and the threaded hole in the cross bar line up.

Retrieve the bolt from the safe place with your fingers and insert it through the drain cover hole and into the threaded hole.

With your finger and thumb give the bolt a few turns clockwise so it starts to enter the threaded hole without any problems. Note: If you experience any resistance when turning the bolt clockwise it may be that the threads have become crossed or it may be that there is some grit obstructing the hole.

Unscrew the bolt, clear the hole if necessary and try to insert the bolt again. You may need to put a little dab of petroleum jelly as a lubricant onto the shaft of the bolt to help it engage in the hole.

Pick up the screwdriver and continue tightening the bolt by turning the screwdriver clockwise until the bolt has screwed in all the way, the bolt head is tight against the drain cover and you can no longer turn the screwdriver. Note: Do not over tighten the bolt or you may damage the threads or deform the drain cover.

  • Wash and dry your rubber gloves and tools.
  • Rinse the shower tray to remove any trace of contaminants.
  • Wash your hands.

I haven’t got a very strong stomach are there any other ways I can unblock the shower drain?

If the method we just talked about was a bit more than you could handle, there are some other ways to unclog the drain. Some of them don’t always work and if they do, can take a long time.

Boiling water. The simplest way to get rid of the grease and soap contributing to the blocked drain (unfortunately it won’t do anything to the hair so afterwards you may still have the beginnings of another blockage) is to pour boiling water down the drain. Simply boil up the kettle or a saucepan of water and pour slowly, a little at a time, down the drain hole. Be careful not to splash any boiling water on your skin as it can cause a very nasty scald. Only use boiling water if you are certain that the drain pipes are metal. If they are PVC pipes then boiling water may damage the joints or deform the pipes. The hot water will dissolve the soap and grease and wash those items away. Unfortunately, as I said earlier, the hair won’t be affected and will remain, ready to form another blockage.

Coat hanger. We talked about this in the detailed unclogging method. But it is such a good tool that I will mention it again. You don’t even have to remove the drain cover to use this. You can insert the hook through the openings in the cover and do a reasonable job of removing the hair.

Baking soda and vinegar. First of all don’t let anyone tell you that vinegar and baking soda are not chemicals. Of course they are, it just so happens that they are edible and not as dangerous as other chemicals. Measure about half a cup of baking soda (also known as sodium bicarbonate or bicarbonate of soda) and mix into a thin paste with a little water and pour this down the drain. Leave for a while. Measure half a cup of vinegar (any vinegar will do but as we aren’t going to cook with it, I would suggest the cheapest) and pour that down the drain. Although the chemical reaction that happens between the acid vinegar and alkaline soda is quite spectacular (that is the fizzing and bubbling you can hear) all that is happening is that carbon dioxide is being released as a by-product of the reaction.

The acid and alkali separately will help to dissolve the blockage but the carbon dioxide provides agitation to dislodge any loosened pieces. If you prefer, especially if there is water already backed up in the shower tray and drain, you can mix the two substances together in a mixing bowl or jug. When the chemical reaction starts to take place, pour the solution down the drain. There should be enough acid and alkali available at the start of the reaction to do the job. Either way, leave the liquid in the drain for about two hours or preferably overnight before rinsing the drain through with fresh water. Remember it isn’t the fizz and bubble that is dissolving the blockage, that action just provides agitation. It is the action of the individual chemicals working separately on the blockage that does the job.

Dishwasher detergent. Dishwasher detergent is very good at dissolving organic matter (look how clean your plates become). Pour some liquid dishwasher detergent down the drain followed by some very hot water. Allow the mixture to stand for an hour or so. The detergent will dissolve the hair and other organic material in the blockage. Rinse the drain with hot water.

Bleach. Pour ordinary household bleach down the drain. The bleach will dissolve the hair and other blockage materials. Leave for a couple of hours and then rinse through with clean water. Note. Wear protective gloves and safety spectacles when handling bleach. Avoid breathing the fumes and avoid spills onto clothing or skin.

Cable tie. This is a variation on the wire hook idea. Take a 10” or 12” cable tie and cut notches down the length with a pair of scissors. Poke the tie down the drain hole and turn the tie to catch the hair. Pull out the cable tie and the hair will come too. Repeat this until the drain is clear.

Sink plunger. The nature of the blockage will probably determine how successful the plunger will be, but it is worth a try. Place the rubber cap over the drain hole and depress the handle a few times. This will force air across the blockage and eventually dislodge the solids. If you have problems getting an airtight seal, then either put an inch or so of water in the shower tray or smear the rim of the rubber cap with petroleum jelly. Both methods will help provide airtight seals.

Plumber’s snake. This is also known as a ‘toilet jack’. This tool is basically a flexible auger made up of a helically coiled metal wire fitted either to a manual handle or an electric motor. The operator pushes the snake down the drain and starts to turn the handle which rotates the wire coil. The coil does a number of different jobs.

  • If the blockage is a dense but shreddable mass such as hair or string, then the coil will cut the lengths into short manageable pieces.
  • If the blockage is unable to be cut then the coil will tangle with the blockage and can be removed by pulling the snake free of the drain.
  • As the coil rotates within the drainpipe, the wire will scrape and clean anything from the pipe walls.

Use proprietary chemicals. Supermarkets and hardware stores stock many different brands of drain cleaner. Read the label and choose whichever is the most suitable for your blockage. Note. Always follow the manufacturer’s instructions exactly and dispose of empty bottles responsibly. Wear rubber gloves and avoid contact with skin. Wear protective spectacles. Using chemicals is usually a quick, easy and affordable way of unclogging a drain.

Call a plumber. If you can’t face taking your drain apart and are not confident with dangerous chemicals, you can always phone a plumber. This is the most expensive method of unblocking a drain and if you have a choice, only call the plumber as a last resort. Having said that, if you use a plumber you are guaranteed to get your drain unblocked.

What materials and tools do I need to have ready?

When you find you have a blocked shower drain (or any drain really) make sure you have everything to hand so you don’t need to go out shopping. Below is a list of everything you might need that was mentioned in the last section. In my experience you may have to use more than one method to finally unblock your drain so it is worth having the option to use a few of these methods.


  • Slot screwdriver
  • Crosshead screwdriver
  • Long nose pliers.
  • Craft knife
  • Safety spectacles
  • Rubber gloves
  • Wire coat hanger or stout wire to bend into a hook
  • Kettle or saucepan
  • Sink plunger
  • Plumber’s snake
  • Cable tie
  • Scissors
  • A phone (to call a plumber)


  • Baking soda
  • Vinegar
  • Dishwasher detergent liquid
  • Domestic strength bleach
  • Proprietary drain cleaner

How can I stop a blockage occurring again?

Prevention is always better than a cure and a clogged drain is no exception. Whatever you do, always try to prevent your blockage in the first place.

A drain protector is a good thing to buy

The protector is like a perforated disk which fits over the drain hole in your shower tray. The tiny perforations allow water to drain through but prevent any solids from ending up down the drain. Not only will hair be caught, but also lumps of solid soap and other solids. They are usually constructed using a perforated, rustproof, stainless steel disc with a silicon rubber rim. The soft rim grips the shower tray to stop the protector from moving around and provides something soft when you stand on it. There are many different shapes and sizes of protectors available to buy including plastic novelty shaped drain protectors. Whatever their shape, the principal of operation is exactly the same. After you have finished your shower, just remove the protector from the shower tray and clean it of any collected solids.

Buy a soap dish

As solid soap gets used it becomes soft and bits of the bar become loose and break off. If the soap has fallen into the shower tray there is a good chance that the lumps of soap will become washed down the drain and into the clump of hair already lurking below. Try to keep the soap safely in a soap dish when not being used and there will be less chance of soap lumps finding their way down the drain. Not only that but a slippery bar of soap under your feet is not the safest way to have a shower!

Clean the drain cover after every use

Train the people in your household with long hair to remove any visible hair left in the shower tray or caught in the drain cover immediately after having a shower. Even though you won’t prevent all hair from washing into the drain, you will get a high proportion of it which will help prevent blockages.

Use liquid soap

To prevent lumps of solid soap from adding to the blockage in the drain, always use shower gel or some other type of soft soap. Although the suds and scum from liquid soap will still become caught in the hair, there will be less chance of a blockage forming.

Rinse the shower tray

After having a shower, remove any scum or soap particles in the tray by rinsing the area with hot water from the shower head. This will help dilute the scum and stop the soap from solidifying until it has travelled past the shower tray drain outlet.

Only wash bodies

This may sound silly but it is quite common for keen mountain bikers to wash the mud from their bikes in the bath or shower. Even though the shower spray is very good at removing mud, you will be washing mud, leaves and all kinds of solid material into the drain. If your shower drain wasn’t blocked beforehand then it probably will be when your bike is clean. Even something as innocuous as washing a pair of socks in the shower can cause problems when the fluff and wool particles become lodged in the clumps of hair. Only wash bodies in a shower cubicle!

How much will this stuff cost?

The cost of buying most of the items listed previously will be negligible compared to the cost of calling out a licensed plumber. The following list shows the kind of money we are talking about and represents an average. I am sure you can find some items cheaper in your local discount store or you may already have some of them in your toolkit or kitchen cupboards.

Screwdriver$6 each
Long nose pliers$6 each
Craft knife$2 each
Safety spectacles$4 each
Rubber gloves$6 for 3 pairs
Wire coat hangernegligible
Sink plunger$5 to $20
Plumber’s snake (aka flexisnake)$5
Cable ties$8 for 100 pack of 12”
Scissors$10 for pack of 4
Bicarbonate of soda$16 for 1lb tubs
Vinegar (distilled white)$7 for 1 gal bottle
Dishwasher liquid detergent (gel)$6 for 75 oz. bottle
Bleach (concentrated)$6 for 64 oz. bottle
Drain cleaner $12 for 32 oz. bottle
Drain protector$5 to $13
Soap dish$3 to $30

What if I want to call in a contractor?

As we have said before, a contractor should never be called in except as a last resort because it is so easy to clear most blocked shower drains. If however, you are unable to open your drain, or clear the blockage in any other way then you will have to resort to a contractor.

Maybe you have been able to open your shower drain and find that the blockage isn’t a normal clump of hair. Your pipes may be very old and deteriorating to a point where they have collapsed. In this case you will need to have at the very least new drain pipes and at the most a new shower unit.

In practice, if your shower drain pipes are so old and decrepit that they are collapsing it probably means that you need to upgrade the complete shower unit as well, so for a few extra dollars you may as well have the entire job done while the upheaval is going on.

For any work involving mains water, water heating or water drainage you will need to call a licensed plumber. If you decide on having a new electric shower, which may need a new power cable installed, you will need a licensed electrician as well.

Work involving water and electricity always need a fully licensed and insured contractor who has the specialist knowledge required to do the job.

Blockages in your shower drain (as well as any other drain) vary in severity from:

  • reducing the speed of draining,
  • to a full blown blockage.

It is always better to clear the partial blockage at the start before the drain becomes blocked completely. If you can do the job yourself then that would be great and would probably only take an hour of your time and probably about $20 for buying a plunger and a bottle of drain cleaner.

If the blockage or drain collapse is outside your home then the problem is very serious. It could be caused by tree roots invading the pipe attracted by the presence of water. If this is the case then you may have to hire a CCTV drain unit to come and probe the sewer. These operatives are able to remotely view the inside of the pipes and see where any collapse or damage has taken place. Once the location is confirmed then excavation of the ground will be needed to expose the damaged pipe. If the damage is caused by corroded pipes then all that will be required is to replace the damaged sections and reinstate the ground. If the damage has been caused by tree roots then the roots will have to be removed and possibly have the tree cut down. The cost of reinstating the ground, repouring concrete and removal of tree stumps will add considerably to the underlying cost of removing the blockage.

Sometimes the blockage (although very rare in the small 2” pipes directly connecting to the shower tray) may be caused by the presence of a dead animal such as a rat partially or fully blocking the pipe.

If you leave the blockage alone until it becomes really severe then you may have to hire a plumber to come and do the job for you. Plumbers usually charge a minimum call-out fee equivalent to one hour of their time. This is to cover their time and transport costs if someone calls them out for a simple 5 minute job. Plumber’s hourly rate will vary depending on the area in which you live, but will be in the region of $45 to $150 per hour.

On top of this you will have to pay for the plumber to do the job itself. This will vary depending on what he finds when he opens up the drain. If the pipes have collapsed then you may need to remove the shower completely and replace all the pipes back to the main sewer pipe or if it is a simple blockage then it may just take an hour of his time with no charge for materials. The cost to unclog a simple blockage may cost in the region of about $80 or as much as $500.

These costs can be summarised as follows:

ItemAverage CostNotes
Plumber (call-out charge)$50 approx.
Plumber (hourly rate)$45 to $150 per hour.
Cost to unblock a shower drain$80 (low end) to $500 (high end)
$130 to $300 typical price range
$200 national average
Plus materials
Cost to replace a shower unit$200 (low end) to $10,000 (high end.
$1,100 to $5,500 typical range.
$3,200 national average
Including materials

The factors that will affect the cost of using a plumber will be:

Regional variations. Different parts of the country and the affluence found in those areas will affect the plumber’s hourly rate.

Seasonal variations. If you live in an area that has harsh winters then a plumber will be very busy during that time with frozen pipes and faulty heating systems. He will therefore probably charge more for his time. This will affect his hourly rate.

How bad is the blockage? A blockage may be something simple like a mass of hair and grease which only requires a few minutes to rectify or it may be something as bad as a blockage in the main sewer or a collapse of the drain pipe.

How many blockages you have. Having one blockage affects the flow of water down a drain pipe and therefore reduces the natural rinsing effect of flowing water. This may result in another blockage further down the pipe. If you are really unlucky the blockages may occur all the way down to the main sewer. That situation would be very difficult to resolve and take a long time to fix.

The cause of the blockages. If the blockages are caused by hair, scum or grease then the remedy is fairly straightforward. If the blockage is caused by corroded or collapsed pipes then the remedy will be to replace the pipes from the shower to the main sewer. This may require a lot of dismantling and lifting of flooring in order to get to the offending pipes. Not only will the costs incurred be labour but will also be the cost of materials as well. If the pipes have corroded or are collapsed then the age of the shower system may have a bearing on the cost as spares may no longer be manufactured for that model. If this is the case then it would probably be more cost effective to install a new system while the upheaval is ongoing.

So when will I know whether to call a plumber or not?

The problem may be a major job but more than likely it will be a simple task that anyone could fix. Most blockages are easily remedied with boiling water, drain cleaner and a sink plunger. It is often highly unlikely that using only one of the DIY methods mentioned earlier will be enough to clear the blockage. Usually two or three methods combined will be what you need to try.

If you have tried everything yourself or if there are other symptoms such as blockages in other appliances like the sink and the toilet then you will need the specialist knowledge and skills of a plumber. Do not delay in asking for help as it will only become worse if you do nothing about it and it will subsequently cost much more in the long term.

Can I get any help with the cost of all this?

Unfortunately the householder is responsible for all drainage issues occurring on private land or until the drain reaches a specific location.

If the damage is to your own water or sewer pipe then you are responsible for the condition of the pipe and any breakage up to where your pipe connects to the public sewer. It is therefore very important to establish the location of any blockage so that you can determine who is responsible for the repair.

Safety concerns

There are a number of different issues involved when dealing with blocked drains.

Chemicals. When dealing with chemicals used in the unblocking of drains you will be handling substances that dissolve and corrode organic matter. The organic matter should be the hair, grease, skin and soap causing the blockage, but unfortunately the human body is also made of organic matter.

Therefore when dealing with acids, alkalis, bleach, ammonia and any other chemical involved in drain cleaning it is very important to protect your skin from contact with the substance. Not only your hands are at risk but also splashes can occur to your face and eyes and onto your clothes. Some substances can be very aggressive and emit toxic fumes when released into the drain system. The empty bottles and containers can still contain traces of the chemical so they will still need to be handled carefully even when empty.

Risk of infection. Drains and drain pipes carry waste materials away from our homes. As such they can be a breeding ground for many harmful bacteria and insects. Once again, contact with the skin must be kept to a minimum as must any splashes to the mouth, face, eyes and clothes.

Both these hazards must be considered when working on drain blockages. The risks and their appropriate counter-measures can be summarised into a few simple rules;

  • Wear protective gloves.
  • Wear protective spectacles or goggles.
  • Wear a face mask suitable for toxic fumes.
  • Work in a well ventilated area.
  • Cover ordinary clothes with coveralls or an apron.
  • Avoid splashes anywhere.
  • Wash hands after finishing the work.
  • Clean the work area after the drain has been covered.
  • Do not smoke, eat or drink while working.
  • Dispose of contaminated substances to a suitable waste receptacle.
  • Dispose of empty chemical containers according to your local and national environmental codes and regulations.
  • Always read the label on the containers and follow the manufacturer’s instructions in the use of the material and in the disposal of the containers.
  • Keep children and pets away from the working area and the chemicals.

Video resources

To finish

Today we talked about what to do when you have a blocked shower drain. We discussed the causes of the blockage, precautions to take to prevent blockages in the future and ways that we can clear the blockage ourselves. There were a few DIY tips on what you can put down the drain to help unblock the pipe but we also considered what would happen if we couldn’t unblock the pipes ourselves. It is in cases like that when a plumbing contractor is the correct person to call. We looked at the costs to buy the DIY tools and materials as well as the costs to hire a plumber. I took you through the steps needed to dismantle, unblock and reassemble a shower drain to remove a blockage as well as highlighting the reasons why you should call a plumber if the job was too difficult for us as amateurs to handle. We talked about what the various causes of a blockage could be, from a simple lump of greasy hair up to a collapsed sewer outside your house.

We talked about the safety considerations of dealing with toxic and aggressive chemicals, some of them with poisonous fumes, as well as being near and in contact with septic surfaces capable of causing infections in a healthy adult. Following on from this we listed some simple rules to follow to minimise our exposure.

I hope that now you know how to unblock a shower drain and realise that the same methods can be used to unblock any domestic drain. Not only do you know how to do it yourself but you also know when to give up and call in a professional. A licensed plumber may be expensive but if you have tried everything else you can guarantee that a contractor will get the job done efficiently and safely.

Let us know what you think of the information provided in this article.