Measuring tape is a common tool in daily life. We often see the steel tape, construction and decoration are commonly used, but also one of the necessary tools for the family. Also includes fiber tape measure, tape, waist ruler and so on.
Luban ruler, Feng Shui ruler, Wen Pan ruler is also belong to steel tape measure. The "inner core" of the tape measure, which has a small piece of steel in it, acts like a spring. You may think so, is the toy pistol trigger on the top of that, used to "blow" the bullet that with the small wire, pull out when the force is bent, loosen the external force (refers to the pull force, and the friction is smaller, smaller than the small steel wire elasticity) disappear, so automatically bounce back.
And the part of the tape that has a folding on the front of it is working so that the tape is stuck outside so it doesn't shrink completely. At first he is loose, pulls out after he becomes tight, after letting go, it should have a recovery process, so then automatically bounce back. He is the first inside is loose, pull the time is tight, there is a stretch between, and then loosen the natural bounce back.