Zippers are usually the reason people chuck a garment in the trash, yet fixing a broken zipper is usually a fairly simple endeavor. There are several reasons a zipper won't stick together. Either the head has been broken, and the teeth are misaligned, some of the zipper stitching has slipped, causing the teeth to be misaligned, or the head and pull tab have broken or warped, causing the teeth to malign when you pull the tab of the zipper.
Things You'll Need
Needle and thread
Replacement zipper head, zipper stop and zipper tab
Fixing a Zipper with a Broken Zipper Stop
Stretch the garment out onto a flat surface and make sure your tools are easily accessible. You will have to see why your zipper won't align, so determine this by assessing the damage to the zipper.
Pry the flathead screwdriver under the zipper stop. It should pop right off with a little force.
Move the zipper tab down to the bottom and see if it moves correctly, up and down with no problems. If it does, and all of the teeth align, then add another zipper stop to the bottom by placing both halves in the correct spot and tapping them lightly with the end of the screwdriver so the two parts of the zipper stop join together.
Fixing a Zipper by Replacing the Head and Tab
Examine the zipper head and tab. It will be very obvious if this is broken, since it won't budge from the teeth of the zipper.
Pry the flathead screwdriver under the zipper stop. It should pop right off with a little force. Separate the teeth of the zipper and gently pull them through the broken zipper head.
Use the screwdriver or the pliers, if necessary, to pry off the head. Be very careful not to break the zipper teeth. Once removed, slide the head off so you just have the teeth and tape of the zipper on the garment.
Smooth out the zipper, pushing the two halves slightly together. Slide the new end of the zipper head onto the zipper, making sure it works correctly. It should easily zip up and unzip the zipper. Refer to step three in the above section to add the zipper stop or sew one into place using the needle and thread. Do this by sewing over the tape of the zipper, right up to the teeth so the bottom of the zipper head cannot slide off. Either method will keep the replacement zipper from sliding off the end.
If you determine that your zipper isn't sticking together because the teeth are broken, then the zipper will have to be replaced.