set square
Pixiv
Twitter
Bluesky
Weibo
Lofter
Tumblr
A triangular ruler used in engineering and technical drawing, with the aim of providing a straight edge at a right angle or other particular planar angle to a baseline, commonly seen as 90°-45°-45° or as 30°-60°-90° shapes. Also known as a "triangle" or "drawing triangle" due to its triangular shape.