Fig 1How a zip closesHover or press ← → to pull the sliderpart open · 3 of 10 pairs hooked
The pair of teeth hooking (or unhooking) at the throat of the YSlider, upper wing cut away: two arms, one throat, the wedge between the armsEvery tooth carries a hook on the face toward the top and a hollow on the face toward the bottom, and the two rows sit half a tooth out of step. Pushed straight together they jam: each hook strikes the tip of the tooth it should enter. Pull the slider up and its Y feeds the rows down two arms at 12° each, so the teeth arrive tilted with their gaps opened; where the arms meet, the throat swings each tooth square and its hook drops into the hollow of the tooth beside it, and a hooked row can't be pulled straight apart. Pull it down and the wedge between the arms prises the rows apart, tilting the teeth until the hooks lift out. The sprung clamps take up the tape as the opening shortens.