Speed Square

Speed Square, a registered trademark of the Swanson Tool Company, is the common brand name for a family of tools also called rafter squares, rafter angle squares or triangle squares: a multi-purpose triangular carpenter's tool used for marking out lumber. Its triangular body combines many of the functions offered by a combination square, a try square and a framing square in one compact tool, and carpenters use it to make basic layout measurements, to mark angled or square lines on dimensional lumber, and as a guide for a hand saw or circular saw making short 45 or 90 degree cuts. Although Speed Square itself is a trademarked brand name, the tool's design is generic enough that it is also known and sold under its other names, and it remains one of the standard layout tools a working carpenter carries.