Abstract: A cylindrical square for inspecting the angular relationship of a test surface to a vertical support surface on a vertical support member. The flat surface being intended to be perpendicular to the test surface, a dial indicator having a sensing member and a supporting member supported on said support surface. Said dial indicator support being adapted to have a dial indicated thereon to be slid along the top of said cylindrical surface of said cylindrical square whereby the dial indicator will indicate errors in the angular relationship of the vertical surface to the flat test surface.