This is the one and only Speed Square, invented by our founder in 1925. This unique tool is actually five tools in one: a try square, a miter square, a protractor, a line scriber, and a saw guide. The Speed Square is constructed of durable heavy-gauge aluminum alloy. Includes markings for Swansons One-Number MethodSM of rafter layout, and is packaged with the Swanson Blue Book of Rafter Length and Roof Construction. Look for the Diamond.