About This T-SquareBoth the aluminum ruler and polycarbonate plastic head are metered for measuring both ways. The ruler also has measurements on both sides, for right-handers and lefties. Available in several sizes. Aluminum T-square with a blue, high-impact steel headRuler measures to 16th of an inch, head to the 8th. Crafted from standard gauge aluminum. 1.5inch wide Aluminum ruler. Available in plenty of sizes.