There are lots of ways to keep your coats and pants and sweatshirts warmly wrapped around you, like buttons, snaps, hooks, and bowties. Then there are zippers, which are just as helpful as the other ways, but slightly more mysterious. How do they work?
A zipper track is made up of dozens of teeth, each of which combines a hook and a hollow. The idea is to latch every hook on each of the two tracks into a hollow on the opposite track. The latching mechanism, called the slide, is just a collection of wedges. As the slide moves up the zipper, the two teeth strips must enter at a specific angle. As the strips move through the slide, the slide’s inclined edges push the teeth toward each other. The strips are offset from each other, so each hollow settles onto a hook in sequence. For this to work properly, each tooth must be exactly the same size and shape, and they all must be perfectly positioned on the track.
