€¢ Special alloy aluminum extrusion for the blades and tongues of Dry Wall T-Squares.€¢ The toque and blade are attached with four (4) stainless steel rivets to assurepermanently set 90° angle.€¢ Numbers and graduations are easy to read.€¢ Dry Wall T-Square are offered in Regular for the Craftsman and Home Owner, and Heavy Duty for the Professional.