Johnson's 16" x 24" arc angle framing square is everything a builder needs to get their work done quickly, efficiently and accurately. Features scribe notches for rough layout of arches in doors and windows, holes for mechanical piping or general layout of arcs and circles. It includes graduations in 1/8", 1/10", 1/12", 1/16" and 1/100", as well as octagon scales, rafter tables, and brace tables, making it useful for any number of different jobs. This framing square's aluminum construction makes it conveniently lightweight while also keeping the tool safe from rust.