The ingeniously simple speed square is the most practical and useful hand tool for any carpenter or do-it-yourselfer.

Also called a rafter square, this multi-purpose triangular carpenters’ tool packs so many features into such a small tool that at first glance it might be confusing how to use it. 

So, we’ve broken down its five uses for you:

Hands placing a speed square on a piece of lumber on a work table.
Make accurate 90-degree or 45-degree cuts by lining up the saw with the edge of a speed square. (3 Echoes Content Studio)

1. Make accurate cuts. Because of its triangular shape, a speed square is great for making square crosscuts or 45-degree lines. Simply line up the edge to a board to cut the right angle every time.

Finger pointing to the 30 degree angle mark on a speed square
Pivot the corner of a speed square to mark angles on a board. (3 Echoes Content Studio)

2. Mark angles. A speed square has a pivot point, so you hold it against the edge of the board and rotate it to mark any angle. For example, let’s say we want to mark a 30-degree angle. Simply hold the edge of the speed square against the edge of a board, then pivot it to line up with the 30-degree mark on the speed square. 

Inserting a pencil into a quarter-inch notch on a speed square
Place a pencil in the quarter-inch notch, then slide the speed square along the board to draw a straight line. (3 Echoes Content Studio)

3. Use it as a scribing tool. Let’s say you want to make a parallel line one inch from the edge of a board. A speed square has quarter-inch notches on its inside, so you can put your pencil in the one-inch notch and slide it along the board. Then, you’ll have an even line one inch from the edge.  

Pencil on speed square to create a straight line on a board
The diamond cutout is three and a half inches from the edge, the same width as a 2-by-4. (3 Echoes Content Studio)

4. Mark the width of 2-by-4. A speed square has a diamond cutout exactly three and a half inches to the edge of the square, which is exactly the width of a 2-by-4. So if you put your pencil in there and slide it along that line, this will is exactly the width of a two-by-four. 

Using a speed square as a saw guide
Use the straight edge as a guide for clean cuts. (3 Echoes Content Studio)

5. Use it as a saw guide. Probably the most useful and obviously practical application of a speed square is as a saw guide. Just take the square, hold it against the board’s edge and guide the saw right against the square. You’ll get a straight cut every time!

Further Reading

Editorial Contributors
Joe Truini

Joe Truini

Radio Show Co-Host

Joe Truini is a contractor, author, and the host of “Simple Solutions” on Today’s Homeowner TV and the weekly Today’s Homeowner radio show. He has worked on both large commercial projects and residential remodeling, and has written for national publications such as This Old House and Popular Mechanics. He has also written eight books, including three best-selling shed-building books. Joe lives in Connecticut with his family and enjoys hiking, traveling, and baseball in his spare time.

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