Common Uses for a Layout or Speed Square

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Commons uses for a Speed Square or layout square other than marking and cutting roof rafters and stair stringers.

One of the most useful carpentry tools invented after the hammer, level, and saw, is the layout or Speed Square. The Speed Square is the trade name for the tool invented in 1925 by carpenter Albert J. Swanson and is the more commonly used name for the tool. The triangular-shaped square was originally developed to provide a faster, more accurate way to mark roof rafters for rough framing and carpentry.

Layout or Speed Square

Originally Speed Squares were made of steel, but as the years passed they have been made out of aluminum and also plastic. They typically come in two sizes, the standard 7-inch and the 12-inch version which is able to layout stairs. Although the tool is designed with coarse markings, the measurements of lengths and angles and very accurate. The design is well suited to framing and rough carpentry with large clear numbers and notches. The thickness of the metal is also important when working with heavy framing studs, floor joists, and roof rafters.

Speed Squares come is several sizes with 7-inch and 12-inch being the most popular.

Aside from the more complicated roof rafter applications, speed squares have multiple uses such as a Try Square, Miter Square, Protractor, Line Scriber and a Saw Guide.

Try Square

The most common use of the Speed Square is to mark square lines at precisely 90 degrees to the board’s edge. In this way the layout square takes the place of the combination square, shown below. Since the tool has a fence running along one edge you can quickly and accurately hold the tool against a board’s edge while marking lines along the square’s side.

Combination Square

This is important when laying out studs on wall plates, positioning floor joists on decks and laying out stair stringers for staircases.

Use a speed square to mark simple cross-cuts.

Miter Square

Because the Speed Square is an isosceles right triangle (Two sides are of equal length), the diagonal edge is machined precisely at 45 degrees to the square’s fence. There are no adjustments required or guides that can be moved accidentally. Holding the fence tight against the board allows you to use the square’s diagonal edge to draw a 45-degree line.

You can use a combination square also, but the fence is much shorter which can lead to imprecise markings.

Use it as a miter gauge 45-degree cuts.


Reading, laying out and marking angles typically requires a protractor or a sliding-bevel square, or both. The Speed Square has degree graduations stamped along its diagonal edge, so reading and marking angles is easy.

At the corner of the square, near one end of the fence, is a pivot point, and it is clearly marked by the word “PIVOT” cast into the tool. Along the diagonal edge are lines, each representing one degree, ranging from zero to 90. 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. Now draw a line along the square opposite the diagonal edge.


Use the speed square as a protractor to mark an angle cut.

The Speed Square also has separate graduations for marking both common roof rafters and hip and valley roof rafters. The square can accommodate roof rises ranging from 1 inch of rise in 12 inches of run, to 30 inches of rise in 12 inches of run.

Line Scribing

Another useful, but often overlooked features of the Speed Square is line scribing. There are two rows of notches machined into one of the square’s slots. The notches in each row are precisely spaced ½ inch apart, but the rows are staggered ¼ inch in alignment, effectively providing a notch every ¼ inch.

To mark a parallel line, press the square’s fence tight against the board’s edge, and then place the pencil tip into the appropriate notch. Now 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 that’s perfectly parallel with the board’s edge.

Saw guide

One of the most common uses of the Speed Square is not as a precision square or protractor, but as a guide for saw cuts. Place the square flat on the board, with its fence tight against the board’s edge. Slide the saw shoe up against the square, and make the cut. Because the Speed Square is thicker than a framing square or combination square, the saw slides along the square which increases accuracy and safety.

Framing Square

You may need to make a few test cuts before feeling comfortable, but before long you’ll be able to make perfectly square crosscuts. Just be sure to hold the square securely in place, and keep the saw shoe pressed against the square throughout the cut.

Use the square as a guide for your circular saw.

The safest way to use the square as a saw guide is to place it on the far edge of the board so the square and board are pulled towards you while pushing the saw away in the opposite direction. You can use the layout square on the near edge if you clamp it to the board, or if the board is narrow enough to hold onto the far edge with your fingers.



Jerry Walch
Posted on Oct 14, 2011
Posted on Oct 14, 2011
Roberta Baxter
Posted on Oct 14, 2011
Francina Marie Parks
Posted on Oct 13, 2011