A speed square, also known as a rafter square or triangle square, is a versatile measuring and marking tool used primarily in carpentry and woodworking. It is shaped like a right-angled triangle with a hypotenuse, two legs, and various markings and features.




Here are some key features and uses of a speed square:

Measuring: The long edge of the speed square is called the hypotenuse, which is typically 7 inches (18 cm) long. It can be used to quickly measure lengths, angles, and make square cuts.


Squaring: One leg of the speed square is shorter than the other, creating a 90-degree angle. This allows you to quickly determine and mark square or perpendicular lines.


Angle measurement: The speed square has degree markings along the hypotenuse, allowing you to measure and mark angles. It commonly includes 0 to 90-degree markings, with additional features like protractor scales for more precise angle measurements.


Roofing applications: Speed squares are particularly useful in roofing projects. They often feature a ridge on the hypotenuse, which allows you to quickly determine roof pitches and make accurate cuts for rafters, stairs, and other angled elements.


Layout and marking: With various measurement guides, notches, and scribe lines, a speed square assists in marking cut lines, creating parallel lines, finding center points, and transferring measurements.


Other functions: Some speed squares include additional features like a built-in level, adjustable fence, or slots for attaching a saw guide or scribing lines.

Speed squares are widely used by carpenters, construction workers, and DIY enthusiasts. They provide quick and accurate measurements, help maintain squareness and precision in various woodworking tasks, and simplify the layout process for cutting and assembly.