The two acute angles of the isosceles square are 45 °. Two identical isosceles right triangle rulers can form a square or a larger isosceles right triangle. The two right-angle sides of an isosceles square are equal in length.

The multi-function triangle ruler is a circle drawing mechanism composed of a rotating ring and a rotary table at the two sharp corners of the original triangle ruler, a needle-shaped angle drawing mechanism at the protractor, a frame at the bottom edge, and a slot rail in the frame. The slot rail is equipped with a positioning mechanism composed of a distance plate, elastic material, slide plate and a parallel line drawing mechanism composed of a slide block embedded in the slot for sliding.