The most common use of the Speed Square is to mark square lines at precisely 90 degrees to the board?s edge. This job is greatly simplified by the fact that the tool has as a lipped fence running more... ...less

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.

The speed square is a triangular-shaped measuring tool that is made of metal. It has many applications and may be used on roofs, to measure angles, mark lumber, create perpendicular lines, or to simply perform a quick measurement.

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. And when building cabinets and other “boxes,” the Speed Square is handy for aligning two pieces at a right angle during assembly.

This is another essential but simple tool that won’t break the bank—you can pick one up for $8. Every pro has one of these in his tool belt, and for good reason. It’s perfect for quickly marking cut lines on lumber, serving as a guide for cutting with a circular saw, and laying out angles for rafters and stairs. (Speed Square is actually a trademarked name for the product. The generic, and less popular, names for it are angle square, rafter angle square, and square layout tool.)

I bought my first Speed Square about 20 years ago for my first construction job and have used it repeatedly ever since. The numbers are a bit faded and the tool has its share of dents and dings, but it has outlasted three tool belts. It’s worth your dime to buy a metal square, since their starting price is about the same as the plastic ones that always end up breaking.