The Swanson Speed Square, model S0101, is a versatile carpentry tool first developed in 1925. This durable, die-cast tool combines five functions: try square, mitre square, saw guide, line scriber, and protractor. Constructed from heavy-gauge aerospace aluminum alloy with a matte finish and black-filled gradations for easy reading, it's built for accuracy and longevity. It includes a pocket-sized Swanson Blue Book of Rafter Length and Roof Construction, and features markings for the Swanson One-Number Method of rafter layout. It also has 1/4 in. spaced scribing notches and a Diamond cutout for marking common, hip, valley, and jack rafters, as well as for making square cuts on boards.