How to Use a Speed Square

Speed Square is a trademarked brand name of Swanson’s original triangular design.

A variety of manufacturers offer a similar square, many of which are generically referred to as “speed squares,” much like many people refer to copying machines as Xerox machines.

This article outlines briefly some of the ways to use this versatile woodworking tool.

You will need

  • Speed Square
  • Board
  • Pencil for marking


Try square

  1. The most common use of the Speed Square is to mark the square lines at precisely 90 degrees to the board’s edge. This job is greatly simplified by the fact that the tool has a slipped fence running along one edge, which allows you to quickly, and accurately, hold the tool against a board’s edge while marking lines along the square’s side.
  2. Being able to quickly draw square lines is particularly useful for jobs that require repetitive, accurate markings, such as locating studs on wall plates, positioning floor joists on decks and laying out stair stringers for staircases.
  3. When building cabinets and other boxes, the Speed Square is handy for aligning two pieces at a right angle during assembly.

Miter square

  1. Because the Speed Square is an isosceles right triangle, its long, diagonal edge is machined precisely at 45º to the tool’s fence. There are no adjustments to make or moving parts to get knocked out of whack. Just press the fence tight against the board and mark along the square’s diagonal edge to draw a precise 45-degree line.
  2. You can mark 45-degree lines with a combination square, but its handle (fence) is only about 3” long, which can lead to imprecise markings. The fence of the smallest model of Speed Square is over 7” long, which provides superior support and ensures very accurate markings.


  1. Reading, laying out and marking angles typically requires a protractor or a sliding-bevel square, or both. However, the Speed Square has degree graduations stamped along its diagonal edge, so reading and marking angles is easy.
  2. At the corner of the square, near one end of the fence, is a pivot point. Along the diagonal edge are lines, each representing one degree, ranging from 0-90.
  3. To mark a particular angle, let’s say, 35 degrees, simply hold the pivot point against the board, then adjust the square until the 35-degree graduation aligns with the edge of the board.
  4. Draw a line along the square opposite the diagonal edge. Note that the Speed Square has separate graduations for marking both common roof rafters and hip and valley roof rafters. The square can accommodate roof rises (angles) ranging from 1” of rise in 12” of run, to 30” of rise in 12” of run.

Line scriber

  1. There are two rows of notches machined into one of the square’s slots. The notches in each row are precisely spaced ½” apart, but the rows are staggered ¼” in alignment, effectively providing a notch every ¼ inch.
  2. To mark a parallel line, press the square’s fence tight against the board’s edge, then place the pencil tip into the appropriate notch.
  3. Slide the square along the board, making sure to keep its fence against the edge and the pencil in the notch. The result will be a line perfectly parallel with the board’s edge.
  4. Use this technique to cut lines on plywood or layout lines on framing lumber.