Product DescriptionThe Swanson® Speed® Square was first developed by company founder Albert Swanson in 1925. This innovative tool combines 5 tools into 1: 1. Try Square, 2. Miter Square, 3. saw guide, 4. line scriber, and 5. protractor. The Speed® Square is die-cast for durability and accuracy. Made of heavy-gauge aerospace aluminum alloy, it is built to last. Black-filled gradations stand out against a matte finish for easy reading. The Speed® Square includes the Swanson® Blue Book of rafter length and roof construction and also features markings for using the Swanson® one-number® method of rafter layout. The Swanson® Speed® Square is our most popular product and remains the most trusted square of its kind. Look for the Diamond® cutout for genuine Swanson® products.From the Manufacturer The Swanson Tool SO101 7-inch Speed Square is a popular pocket-sized square that incorporates features of the framing square, tri, miter, and protractor squares. Common rafter and hip/valley rafter scales permit one-number references for all cuts. The square is merely rotated to the proper roof pitch value on either scale to assure the correct angle cut. The slot along the scales will accommodate an adjustable locking pin for repetitive cuts using any 1/4-inch bolt and nut. Comes with a handy, 62-page pocket sized booklet that provides vital instructions, reference diagrams, and tables for the construction of roofs and stairs.