A zipper closes by forcing two rows of teeth into an alternating pattern with a sliding wedge.

The longer version

Each row of a zipper carries a line of teeth, and the slider's Y-shaped channel gathers both rows so a tooth from one side drops into the gap between two teeth on the other. Interleaved this way, the rows cannot separate sideways, because every tooth is boxed in by the ones across from it. The wedge shape of the channel presses them together at the moment they meet.

The idea failed commercially for decades because early versions jammed or sprang open under strain. A later redesign locked each tooth to the tape with a stronger grip and gave the slider a tighter throat. What people misread is that closing is not a latch clicking shut; it is dozens of small interlocks forming and unforming continuously as you pull.

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.