Throwing away your favourite dress or purse just because the zipper is broken is a terrible waste. Repairing a nylon zipper just takes a few minutes, and it might save a vital piece of your wardrobe. Knowing how to fix a broken zipper is very useful -you'll never have to throw away another backpack, handbag, or pair of jeans just because the zipper gets stuck or slides off its track.
Insert the butter knife into the groove on the side of where the pull has come off.
Pry open the space, just large enough so that you can get the zipper in.
Slide the zipper in and push together the opening you pried apart.
Slide the zipper down to the end of its track.
Use a very small amount of liquid soap or butter, and apply it up and down the track on both sides with your finger. Be careful that the material of the garment or handbag that the zipper is on won't be permanently stained by either.
Try sliding the zipper up again a few times. If it doesn't stick, wipe off the butter or liquid soap with a damp cloth.