Take errors and guesswork out of your next drywall job with this heavy-duty 48 in T-square from Johnson. Its extruded aluminum blade and head are a robust 3/16 in T, creating a safer straight edge that prevents your utility knife from slipping, while its clear protective anodized finish will keep your tool safe from rust and corrosion. The JTS48HD T-square features a unique rivet assembly that permanently bonds the head and blade, so that it stays square for life. This T-square was also designed to be easy-to-use. It features thermal-bonded black 1/8 in graduations that are large and bold for easy reading.