Taiwan has lots of earthquakes but also tall buildings like Taipei 101. When building these skyscrapers, architects use strong bolts to hold the floors together. These bolts are like the building's "joints." But how do we know how tight these bolts should be?

From fast trains to big bridges and delicate factory machines, screws and nuts need to be tightened just right. Different tools are used for different jobs. For example, special wrenches measure how tight the bolt is, and some bolts even break off at the end when they’re tight enough.

Making sure bolts are tight enough but not too tight is important. This is especially true for big, strong bolts, which need enough force to hold tight, and for small, delicate screws, which can’t be tightened too much.

Things like oil, rust, and temperature can change how much friction is on the bolt. This can make the tension different from what you expect. That’s why you shouldn’t reuse damaged bolts. In other words, it’s best not to use reused screws, even though this can be hard in car repair.