Set Square 31cm Staedtler Mars 567 31-60 60/30 Degree Set squares, in the shape of right-angled isosceles triangles, are more than just a common tool in geometry class: they are also frequently used in the field of technical drawing. Even in ancient Egypt, similar instruments were used to measure fields. To measure an angle, all you need to do is place the zero point of the set square on the intersection and read the corresponding value on the angular scale Staedtler set squares are available in a variety of sizes to suit your specific needs. They are made of transparent, extremely break-resistant plastic, so they will last a long time even under heavy-duty use. Staedtler also offers versions with or without a removable grip and ink studs. Features: With inking edge. Scale begins directly at the edge. Plastic, translucent blue. Calibrated in mm. Ideal for students.