The main part inside the tape measure is a circular plastic frame. From the front, a tape measure is wrapped around the frame. On the reverse side of the plastic frame, on the inner side, there are spring sheets wound in a circle. One end of the spring leaf is bent into a hook shape and fixed in a small slit in the plastic frame. The other end was bent into a ring and fixed in a small slit in the ruler box. There is a hollow column in the middle of the ruler box with a small slit on the column.

The internal structure has only one axle, and the ruler is wound on the outside, and the ruler is wound on the axle. The ruler can also rotate, but its center is pulled by a spring. When you pull the ruler, the wheel will also rotate with it, and the spring will be squeezed again and again. When you loosen it, the spring will pull the wheel back into place, and then the ruler will follow it back.

Tape measure is a commonly used tool in daily life. What you often see is the steel tape measure, which is commonly used in construction and decoration, and is also one of the essential tools for the family. Divided into fiber tape measure, tape measure, waist measurement and so on. Luban ruler, Feng Shui ruler, and Wen Gong ruler are also steel tape measures.