Swanson Speed Rafter Square combines the essential features of framing, try, miter, and protractor squares into one versatile tool. It includes the Blue Book of Rafter Length and Roof Construction, which explains basic construction principles and provides rafter length tables to assist in your projects. Made from durable aluminum alloy, this square measures approximately 7-1/2" by 7-1/2" by 10-1/2", with precise 1/8-inch graduations for accurate measurements. for carpenters and builders, this tool convenience and reliability in one compact design. Model Number: S0101