This multi-sized ruler features two triangles in one. Use the 45 degree side to cut half-square triangles from strips up to 5-1/2 inches wide, creating half-square triangles up to a finished size of 5 inches. Use the 90 degree side to cut quarter triangles that finish up to a 5 inch finished quarter-square triangle. The math required to cut these angles is incorporated into the easy to read black and white markings. https://youtu.be/Qrl9UypDCFw