There are usually scales on the ruler to measure the length. Some rulers have a special shape such as a letter or a circular hole in the middle, which is convenient for the user to draw pictures. They are usually used to measure the length. They are generally divided into tape measure, vernier caliper, square ruler, and straight edge.
1. Straightedge: with a precise straight edge, used for measuring length and drawing. It is widely used in mathematics, surveying, engineering, and other subjects.
2. “Snake Ruler”: It is a ruler specially used to draw curves.
3. Triangle ruler: It is a right-angled triangle or an isosceles triangle ruler. The right-angled triangle board can be used to draw right angles. It is convenient to draw parallel or vertical lines with a ruler.
4. Slide rule: a calculation tool.
5. Soft ruler: often used to measure parts of the human body.
6. Pull rule: used to measure buildings, furniture, etc.
7. Vernier caliper: used to measure relatively small things.