Gif Central boasts hundreds of funny animated gifs. Only the best of the best make it onto this site, with most of them having an accompanying source. No tumblr-esque one-second-long disappointments. No obscure titles or descriptions.
This is an animated gif that shows you how a common everyday zipper works. As you can see, the teeth on the zipper are positioned in a way that forces them to close down on top of one another as they are brought through the slider body.