What Are The Wooden Pieces That Come With a Canvas? And How To Use Them

If you’ve ever bought a pre-stretched canvas you may have been surprised to find a small bag of wooden pieces attached to the back of the canvas stretcher. A lot of people wonder what they are actually for; this article should help answer some of your questions!

canvas with wooden pieces

Most pre-stretched and primed canvases will have good enough tension to allow you to start painting on them as soon as they are in your hands. Occasionally you may find that the surface has slackened slightly, before or after you have started painting. In most cases, your canvas will come with a bag of wooden canvas wedges (also known as canvas keys), which can be used to tighten up the tension of your canvas if you find it has loosened.

During the painting process, the addition of paint, collage and other elements will burden your canvas with extra weight, which over time can cause the surface to loose its tightness. Environmental factors, such as temperature and humidity, can also cause the material on your canvas to move and shift. If you have completed a painting and find that it is slackening on the stretcher you can use canvas wedges to tighten it back up again.

How to Use Canvas Wedges / Keys

If you have never used canvas wedges before, you can follow the steps below to install them quickly and easily.

1. In each corner of your canvas you will notice some slots cut into the wood.


2. Place each of your canvas wedges into one of the slots in the corners of the canvas. The diagram to the left will help you install them in the right orientation.


3. Before you secure the wedges with a hammer, it is a good idea to place a piece of scrap card behind the wedges so that the surface of your canvas will not be damaged by your tools.

4. Stand your canvas upright and use a hammer to gently tap each of the wedges upwards to fit them securely into the wooden slots, while supporting the rest of the canvas with your free hand.

5. Make sure you use the wedges to move one stretcher at a time, in order to keep the canvas square.

6. Rotate your canvas and hammer in the remaining wedges until you have achieved your desired tension.

Your canvas should now be perfectly stretched!

If you have any other questions about canvases don’t hesitate to get in touch with us in the comments or on social media.

Written by

Gareth Evans

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A passion for sharing the cool, interesting and entertaining art news from around the world. Gareth has created stories about art which have been featured in The Art Newspaper, ArtDaily, The Telegraph and Lonely Planet.
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13 thoughts on “What Are The Wooden Pieces That Come With a Canvas? And How To Use Them

  1. Thanks for sharing these valuable blogs with this blog now I can properly stretch a canvas. This very helpful for me.

    1. Thanks for your comment! Once you’ve inserted the canvas keys into your canvas you’ll need to leave them in place. They’ll keep the corner of the stretcher pushed apart, and removing them will cause the stretcher to move – making your canvas sag again. If inserted properly, they should be in there tight enough that they won’t fall out. They’re a bit like a ‘keystone’ – they’re there to lock the whole stretcher in position.

  2. I’m still confused. Do they lay one way until you hammer them? In other words, The one that goes in horizontally ends up vertical when you are done? They both seem so loose, I’m obviously doing something wrong. Are they simply wedged in, or does the pointy part actually pierce, or bore a deeper hole in the frame until the “canvas key” doesn’t move?? Sorry, I’ve never done this before.

    1. Follow-up: I just watched a video on YouTube. The slots were much smaller. Now THAT makes sense. The slots on my canvas are almost as long as the wooden keys, rendering them, in my experience, useless.

    2. Just follow the instructions on this site
      The angle of the keys marry in the groves. Sometimes keys ate too thin or the groves cand be slightly wide this is down to machining of the timber used if a key is slack there is a simple remedy I use have a roll of plastic electritions tape handy wrap the tape directly above the angle of the key so you get a nice clean layer or 2 of the tape on the key do one at a Tim’s that should stop the keys falling out

  3. Very useful and clear thanks. The picy with the hammer could be improved by showing the hammer acting vertically down against the table; the picy implies that you hammer horizontally which doesn’t work!

  4. Hi Ken Bromley
    Thank you for the very useful guide to putting in the little pieces of wood which are scattered around inside the back of the canvas when it’s unwrapped.I assumed they were to be hammered into the slots but not sure which way was best.Your little article is the only info I have found .

  5. What use are the wedges when the manufacturer puts staples across the joints so that they will not open and when the taper is so long it pokes out of the edge of the stretcher bars? I have had this on so many well known brands of canvas especially Jacksons

  6. The description of how to use canvas keys/wedges does not make clear which way up to insert the keys. On the assumption that the “pointed” end goes in first, Does the long side or the short side sit against the stretcher bar?


    Tony Fagan

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