How to Use a Rafter Square


A rafter square, or rafter angle square, is a measurement tool used in carpentry. It is triangular in shape and combines elements of a protractor, ruler and carpenter's square. It is used to measure and mark lines and angles for cuts, and it can also be used as a cutting guide. A rafter square features measurements including imperial, metric, degrees and a right angle. One of the adjacent sides has a fence that is used to hold the square true to the surface.

Things You'll Need

  • Rafter square
  • Pen or pencil
  • Wood
  • Place the square on the wood to be cut. If you are marking a 90 degree angle, make sure the fence on the square is flush with the side of the wood board.

  • Measure the distance along the wood. For 90 degree cuts, the rafter square fence can be left flush against the side of the wood. For other angles, make a mark at the edge of the wood, then line the pivot of the rafter square with it. Rotate the pivot until you reach the desired angle.

  • Mark the wood using a pen or pencil. Use the rafter square as a ruler. Make sure the mark is dark enough so you can see it when you are cutting.

Tips & Warnings

  • The fence of the rafter square can be used as a guide if needed. This works best for 90 degree cuts. Place the fence of the square along the edge of the wood and run the guide of the saw along the adjacent side of the rafter square for a perfect cut.
  • A rafter square is not well-suited to fine woodworking. The coarse markings make the square more useful for larger projects, such as framing.

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  • Photo Credit New residential construction home framing. image by Andy Dean from
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