rule

Rulers, also known as rulers and scales, are tools for drawing line segments (especially straight lines) and measuring length. There are usually scales on the ruler to measure the length. Some rulers have holes with special shapes, such as letters or circles, which are convenient for users to draw. They are usually used to measure and calculate the length, and are generally divided into tape measure, vernier caliper, ruler and ruler.

Knowledge expansion:

The snake ruler is a ruler specially used to draw curves. Triangular ruler is a ruler of right triangle or isosceles triangle, which is convenient for drawing parallel lines or vertical lines. Slide rule: a calculating tool. Soft ruler: it is often used to measure human body parts.

Ruler: used to measure buildings, furniture, etc. Vernier caliper: used to measure smaller things. In ruler drawing, ruler is regarded as a tool for drawing infinite straight lines. Level: Level is a measuring instrument that uses the principle of liquid level to directly display the angular displacement and measure the deviation degree of the measured surface relative to the horizontal position, vertical position and inclined position.

One of Lu Ban's inventions is that he can correctly draw a right triangle, also called a class ruler, and can tell craftsmen which sizes are irregular and which ones are unlucky according to the rules of divination (geomantic omen). These rulers are still available.

Silk cloth ruler, also known as tailor ruler or cutting ruler, originated from the ruler with class ruler, but it has not been passed down from generation to generation, and has long lost its standard and become another ruler system.

Rulers used in different occasions have different requirements and standards. If more accurate values are required, then higher technology is needed, and they must be produced by machines. Besides the accuracy of numerical value, the second key point is the quality of engraving value. Generally, a protective film will be branded after the value is engraved.

The third point is the choice of materials, which are currently divided into plastic, metal and wooden rulers. Plastic rulers are mainly used by ordinary students to make stationery, metal rulers are more industrial, and wooden rulers are mainly used for teaching.