What’s the Hole in a Safety Pin For?

The Design of the Safety Pin, at a Glance

Before plunging straight into Bafflement Hole, let’s do a rapid-fire rundown of how a safety pin operates, because that gives our world context. At first glance, it looks like a really simple tool — basically a bent piece of wire with a clasp. But it’s so cleverly engineered. This end is sharp (obviously), and the other has this little loop, or a coil, that is where that hole lives.

The coil creates tension. It’s this tension that keeps the pin shut when you close it, so it doesn’t spontaneously pop open and stab you in the thigh during a meeting. The clasp part? That’s all safety stuff — hence the name — so the very sharp end is neatly tucked out of the way. But back to that coil. The shape of it, see, is not because everything inside needs to be kept springy.