IRWIN Tools Drywall Square, Aluminum, 48-Inch (1794476) Irwin Aluminum Drywall Square 48 In Irwin Tools Irwin Aluminum Drywall Square 48 In Thermally bonded graduations with an anodized finish. Aluminum body is durable, rust-proof, and lightweight. This square is used for measuring and marking sheets of drywall, plywood and other building materials.