Jackets typically have tooth zippers. This simply means that they have plastic teeth. A #5 is a normal, medium-sized zipper for a jacket. If you are making your own jacket, you can purchase a zipper at any fabric or craft store. You can also replace the zipper on a store-bought jacket. Zippers can break or stop working for a variety of reasons; typically you can fix them without completely replacing the zipper.
Place the teeth of the zipper into the correct grooves of the slider.
Squeeze the sides of the zipper slider with a pair of pliers. Make sure to do it gently and not to over-squeeze them. You want it to be able to still slide up and down.
Gently pull the slider up and down to ensure that it is fixed.
Pull open one end of the arch that holds the pull to the zipper slider, using a pair of pliers. Be sure not too pull it open too far, or it may break. You just need it open enough to extract the zipper pull.
Slide the zipper pull off.
Place another zipper pull under the arch. This can be a purchased item, a key chain, or a simple thread loop.
Using pliers, close the arch back again.
Rub candle wax on the zipper teeth to help it open and close more smoothly.