Carpenter's Squares

The base of this compact right triangle has a flange that you can butt against a workpiece edge, allowing you to draw a perfectly square cut line or 45-degree miter, and to use the square as a fence for crosscutting. The diagonal edge has markings for laying out rafter, roof trim, and stair angles. 

The speed square, also known as a rafter square or triangle square, is a versatile tool favored by many carpenters. Its triangular shape features a lipped fence that allows it to sit flush against a board’s edge. This type of square is the most common and can be used in all manner of construction projects. Chances are, you’ll end up buying more than one.

“The first square you buy should be a 12-inch speed square,” says Tom Silva, This Old House general contractor. On the job, Silva does most routine carpentry with his speed squares. “I use the 12-inch one as a crosscut fence for my saw and router, and the 6-inch one is always in my apron pocket — it’s especially handy when I’m up on a ladder.”

Speed squares are ideal for:

• Marking 90-degree and 45-degree angles

• Serving as a saw guide for crosscuts

• Measuring and marking rafter angles

• Checking for square on boards and framing

The try square is a fixed 90-degree square often used in woodworking. Its primary functions include:

• Checking the squareness of edges and corners

• Marking perpendicular lines

• Verifying the flatness of surfaces

Cabinetmakers like this fixed square for checking corners and edges, but for most carpentry tasks, a combination square is more versatile

With its long blade, the drywall square is designed for working with large sheet materials. It’s used for:

• Marking cut lines on drywall and plywood

• Serving as a cutting guide for drywall

• Checking squareness on large panels

A drywall square has a 4-foot blade ideal for laying out cut lines on standard-size sheets of plywood, drywall, and other board materials. You can also use it as a guide when cutting drywall.