Why Do Keys Look So Complex?

Imagine your key is like a special toothpick that fits into a specific hole. The holes in the lock are called pins. When you put a normal key in, the pins fall down and block the door from opening. Your special key has bumps that push those pins up just right. Then everything lines up, and click, your door opens! Long ago, people used heavy iron keys with big knobs to open castle doors. Today, we use lighter keys made of brass or zinc. They are strong enough but easy to carry in your pocket.