Paper clips hold sheets together through spring tension in their bent loops of wire.

The longer version

A paper clip is a length of bent spring wire. Forcing the two loops apart stores energy, and once released the wire tries to return to its original shape, squeezing the sheets between the inner and outer loops. Friction between the paper surfaces then stops the sheets sliding out of that grip. The long inner loop spreads pressure along a strip rather than a point.

The wire is usually steel with a coating, chosen because it can flex repeatedly without taking a permanent set. Push a clip too far and it stays bent, because the metal has been stressed past its elastic limit; after that the grip is gone. That limit is why a well-used clip eventually feels loose and lets pages slip.

Where this entry sits

Odd Little Things looks at the ordinary objects people touch every day and the small mechanisms and histories hiding inside them. Buttons, zips, pencils, mirrors, stairs, stamps, packaging, and road signs all get their turn. The full list sits on the Odd Little Things page, where every entry is listed in order.