Egyptian wooden right angle, New Kingdom, (1550-1070 BC). A carpenter's square is a tool for determining, measuring, or setting out right angles, or for testing the exactness of artificers' work, usually consisting of two pieces or arms set at right angles to each other, but sometimes with the arms or sides hinged or pivoted so as to measure any angle; esp. one used by carpenters or joiners. Wooden squares, like the one pictured here, have been found buried ceremoniously in the tombs of master Egyptian builders.