Top stops prevent the slider from coming off the zipper track. There are three types of top stops:

Coil top stops are metal pieces shaped like a claw with three prongs (2 on one side and 1 on the other). They're applied by puncturing through the zipper tape and wrapping the prongs into the coil.

A single hand stitch can also be used as a stop for a coil zipper.

Plastic tooth (Vislon®) top stops are colored metal pieces shaped like a hot dog bun. They clamp onto a toothless area of the zipper tape.

These top stops don't prevent plastic tooth sliders size 5 and larger from sliding off the tape. Use metal top stops instead.

Metal top stops are metal piece shaped like a small "c." They clamp onto a toothless area of a metal or plastic tooth zipper tape.

Despite the name, top stops can be placed on other locations of the zipper track, not just the top.