It work when the zipper pull can't close the zipper together anymore.
I don't really like to replace zipper because they always come out a little bit wavy when I do.
You can save a jacket, a tent, a sleeping bag and many other item.
IF YOU LIKE IT can you VOTE for me in the FIX IT CONTEST thanks!!
Step 1: WHAT YOU NEED
If the zipper pull is really destroy or is made in plastic you need a new one of the same size.
I finded one from an old jacket.
Step 2: REMOVE TEETH
Step 4: ADJUST THE ZIPPER PULL
Whit the pliers close the two sides of the zipper pull, try to make it look like the original shape again.
If your zipper pull is not too worn out you can try to close it directly on the zipper, without remove it.
(if it is made out of plastic, if it is too bended or it break doing this you need to find another one of the same size).