Old 09-17-2000, 09:04 AM
Join Date: Jun 2000
Location: New Brunswick
Posts: 4,404
I was looking at my zipper after reading the YKK marking question. I noticed that it's immpossible to pull the zipper down if the little 'pull-tab' thingie is facing up. Once flicked down, the zipper would basically unzip by itself.

Is there actually a lock on the zipper to prevent it from unzipping itself, or am I imagining things?
Old 09-17-2000, 10:03 AM
Straight Dope Science Advisory Board
Join Date: Mar 2000
Location: With Candy Darling
Posts: 15,989
It's just a trick of the mechanical advantage you get when the lever is facing down - there's no little lock inside or anything.
Old 09-17-2000, 10:51 AM
Join Date: Sep 2000
Location: Duluth, GA
Posts: 1,166
Depends on the zipper. Some zippers do indeed have locks. I've seen two different types:

1) A small projection near the pivoting end of the zipper tab that fits into a hole in the zipper body when the tab's down, engaging between two adjacent teeth of the zipper, preventing it from moving up or down. I see these mostly on jackets, and only rarely on pants -- when I see it on a pair of pants, the zipper teeth are almost always plastic instead of metal.

2) A small moveable cage that fits over the attachment of the zipper tab to the body. When the zipper tab is held roughly perpendicular to the zipper, the cage is lifted up because the tab's axle has a rectangular cross-section, with the wide side parallel to the rest of the tab. I haven't taken one apart to figure out exactly how it works, but I suspect the bottom of the cage has teeth that protrude into the zipper, getting caught between the zipper's teeth, in the same way that the other lock does.

In my experience, the second type of tab is much more common -- almost every pair of pants I have uses that type of lock.
Old 09-17-2000, 01:57 PM
Charter Member
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 77,489
3waygeek's guess is, in fact, correct-- I have taken them apart and saw the protrusion on the bottom end of the "cage", as he calls it. It's great when it works properly (much lower incidence of flies falling open), but it's also yet another thing that can jam up.
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