The Empire® 16 in. x 24 in. framing square (1140) is made of lightweight aluminum that will not rust or corrode. The carpenter square has ARC-SCRIBE™ which is the best solution for marking radii. The aluminum framing square has permanently stamped markings at 1/8 in., 1/10 in. and 1/16 in. graduations, as well as rafter tables.