1. Ruler: Ruler is not a ruler, but a tool for drawing line segments and measuring length. There are usually scales on the ruler to measure the length. Some rulers have holes with special shapes in the middle, such as letters or circles, which are convenient for users to draw.

2. Compass: Compass is a tool for drawing circles or strings in mathematics and drawing, and is often used for ruler drawing. Compasses are usually made of metal and consist of two hinged parts, which can be adjusted.

3. Abacus: Abacus, also known as abacus, is a simple calculation tool invented by our ancestors. Abacus originated in the Northern Song Dynasty, and abacus calculation began in the Northern Song Dynasty. Abacus is a simple calculation tool invented and created by the working people in ancient China. China is a career of abacus.