Assembling a stretcher frame how to guide

Here at Bird & Davis, we pride ourselves on being experts in providing artists with all things stretcher frame related. We cater to artists of all forms, from budding artists to seasoned professionals. One of our strengths is understanding how essential the right tools are when creating a work of art from scratch. This is why we only provide the best handmade, high-quality Stretcher Bars to ensure your canvases can stretch beautifully, allowing you to get creative and build your next masterpiece quickly. 

Although assembling a stretcher frame can seem like a complex challenge, it is a relatively simple process once you break it down. This guide will take you to step by step through how to assemble stretcher frames of different sizes. Check out our informative YouTube videos for each section for a visual aid so you can master each step.

What Are Stretcher Frames Used For?

To stretch your canvas, you will need to use stretcher pieces to create a stretcher frame. The stretcher pieces you choose are paramount and, if anything, just as important as the canvas used to determine the finished product. Shop our range of fine handmade stretcher pieces in various sizes to suit all needs and abilities. Also, check out our best-selling Build a Stretcher service, providing custom frames to suit your needs. 

Assembling stretcher frame guide

Getting Started 

In terms of tools needed to assemble your stretcher frame, the only thing you'll need along with your stretcher frame pieces is a mallet. Next, you'll need to establish if the stretcher frame you are building has six windows, four windows or two windows, as this will mean the set-up differs. 

Building a Stretcher Frame With No Internal Bars

  1. Lay out all 4 pieces together. 
  2. Take two pieces and push the corners together, ensuring the sharp edge is on the back and follows around. If it's a rectangular stretcher frame, you will need two different-sized pieces for this step.
  3. Take the third piece and push it into the opposite corner, turning it round to make a U shape. 
  4. Take the last piece pushing into the last top corners, making a square shape. 
  5. Use a mallet to tighten it up. 

    Building a Stretcher Frame With One Internal Bar (Two Windows) 

    1. Lay out all five pieces in front of you.
    2. Take the two longer pierces with the mortise holes. Push the bar into a stretcher piece, creating a T shape. 
    3. Turn the T shape around, creating an upside-down T shape. Now, take the next longest stretcher piece pushing into the centre of the mortise hole, creating an H shape.
    4. Please take one of the remaining stretcher pieces and push it to the next two available corners (at the top). At this stage, there is no need to worry about the frames being looser, as they can be tightened up with a mallet at the end. 
    5. Take the last piece, and push this into the remaining two corners, creating a two-window shape. 
    6. Lastly, use the mallet on all corners to tighten the stretcher frame. 


      Stretcher Frame With An Internal Bar Each Way (Four Windows)

      1. First, lay out all seven pieces in front of you. 
      2. Take one of the longest outside pieces, and push the mortise bar into the mortise hole on the piece. 
      3. Next, take the other long stretcher bar, and push it into the other mortise hole, creating an H. 

        Assembling a stretcher frame guide

        4. Now, put the half bar into the mortise hole in the middle, leaving the wedge cut towards the outside of the stretcher frame.
        5. The next step is to take the other outside stretcher piece and push it into the next available corner. Make sure you bear in mind to keep the mortise bar (half bar) lined up with the mortise hole.
        6. Now, use the mallet to tighten up the corners.
        7. Flip the stretcher frame upside down.
        8. Now repeat steps 4, 5, and 6 exactly to complete your four-window stretcher frame.


        How To Square Off Your Stretcher Frame

        Once you have a fully assembled stretcher frame, you will need to ensure it's perfectly square, so it's set up correctly for stretching your canvas over it. Now that your stretcher frame is fully assembled, you'll need to ensure it's perfectly tight across every corner.

        1. Stand the frame up, and check each corner, using the mallet to knock any corners into place that doesn't feel tight.
        2. Next, lay the stretcher frame down flat. To ensure the stretcher frame is square, we need to measure the diagonals, as when these measure the same size, we will know they are perfectly square.
        3. Now, take your tape measure across from diagonal corners. Start in the left corner to the right and measure diagonally across (see the YouTube video for a clear demonstration of this to ensure you get it right). 

          Guide to assembling a stretcher frame how to square off 4. Lastly, take the tape measure across to the other diagonal corners from right to left and take the measurements, comparing each measurement against the other. If the diagonals don't match up, this is where you will take your mallet, tapping in the corner of the longer diagonal to even up with the other diagonal corner! Once both diagonals match up in length on your tape measure, you can rest assured that your stretcher frame is completely square! 

          Want More?

          If you are creating a larger frame, such as a stretcher frame with 6 windows, check out the video below:


          Check out our highly popular Build a Stretcher service if you want a custom stretcher frame built to specific dimensions. We also offer bespoke On Site Stretching, where we can attend to your property and remove and re-stretch any piece of artwork onto either your existing frame or a brand-new stretcher frame. Find out more here.

          Still, puzzled? If you have any questions on this, please drop our friendly team a line at, or pop into our store, where we are always more than happy to take you through anything you need guidance on, across anything from stretcher frames and painting solvents to easels, or even just a chit chat! 

          Stretcher frame

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