A Spring Hidden in a Safety Pin
Before safety pins, people held cloth together with straight pins. A straight pin was easy to lose, and its sharp point could stick the person who wore it. An inventor in the 1800s looked for a better way. He bent a single piece of wire into a clever shape, and the safety pin was born.
Look at one closely. The wire is bent into a small coil at one end. This coil is a spring. When you squeeze the pin open, the spring is pushed out of shape. When you let go, the spring pushes the wire back to where it started. That push is what keeps the pin snapped shut.
The other end of the pin has a small cover called the clasp. The sharp point tucks into the clasp, so it cannot poke anyone. To open the pin, you press the point out of the clasp and swing it free. To close it, you push the point back into the clasp until it clicks.
Because it is made from one piece of wire, a safety pin has no loose parts to lose. Parents use them on cloth diapers, and tailors use them to hold cloth in place. A spring and a clasp make a simple tool that is safe to carry.