Swanson Big 12 Speed 12 In. Aluminum Rafter Square

Cast aluminum alloy. Measures 12" x 12" and 17" across the diagonal, which is marked off in degrees from 0 deg. (degree) to 90 deg.. Features scribe bar, notched every 1/4", to lay out parallel lines. Lay-put bar adjusted out to fit out of square corner. 2 adjustable stop pins can be set for proper run and proper rise. Includes Blue Book of Rafter Length and Roof Construction.