The "core" of the tape measure has a small piece of steel in it, which acts like a spring. You can also think of it this way, it is the one on the trigger of the toy pistol, the small wire used to "strike" the bullet, when it is pulled out, it is bent under force, and the external force after release (refers to the force of hand pulling, while the friction force is stronger than the friction force). Small, less than the elasticity of the small wire) disappears, so it will automatically spring back. And there is a folded part on the front of the tape measure, which works at this time, so that the tape measure is stuck outside, so that it does not fully retract. It was loose at the beginning, but it became tighter when it was pulled out. After letting go, it should have a process of recovery, so it will automatically spring back. That is, it was loose in the beginning, and when it was pulled, it tightened, and there was some elasticity between it.

The main type of tape measure is steel tape measure, followed by fiber tape measure. In southern my country and Hong Kong, the tape measure is usually called a soft ruler or a pull ruler. The material is PVC plastic and fiberglass, which prevents the tape measure from being stretched during use.

Leather tape measure is made of glass fiber and PVC plastic, also known as fiber tape measure or soft measure. It is generally metric and inch, which is 150 cm on one side and 60 inches on the other side. Inches is a commonly used unit of measurement abroad, and the size unit of TVs and monitors is inches. And the size of the jeans, also in inches. In China, the commonly used measuring tape is the market size. One side is 150 cm and the other side is 45 inches. Often said 2 feet 1, 2 feet 2 waist, is the city-inch unit.