Ruler, also known as ruler and interval ruler, is a tool for drawing line segments (especially straight ones) and measuring angle length. General ruler set refers to straight ruler, right triangle ruler, obtuse triangle ruler and protractor. In mathematics and drawing, compasses are tools used to draw circles or chords. They are often used for drawing with rulers and compasses.

The compass is composed of a pen head, a rotary shaft, a compass leg, a ruler, a folding leaf, a pen body, a pen tip, a compass tip, and a small ear. The lower end of the pen head is inserted and connected at the upper end of the pen body, the lower end of the pen body is threaded at the upper end of the pen tip, the flush end of the small ear is welded at the middle of the outer side of the compass leg, and the lower end of the compass leg is clamped and connected at the upper end of the compass tip.