1. Make a bottom stop
You want to keep the zippers top stoppers and only shorten it by making a new bottom stop.
First measure the length you need for the zipper in your garment and mark it onto the zipper. Before you cut anything off, you must sew in a new bottom stop for the slider.
Take a sewing needle and a normal sewing thread and sew a few tight loops around the zip where you have your mark.
2. Remove zipper teeth
There are different types of zipper teeth. Some can need to be pulled out (carefully) before you can cut them off and some you can cut out right away. It doesn’t matter how you do it, just make sure that the teeth come out without ruining the material around it.
3. Reinforce the end of the zipper
Start by applying glue to the backside of the end of the zipper and a piece of cloth. Allow both to dry completely.
Glue the piece of cloth on to the backside of the zipper. Apply pressure to make a strong bond using your seam roller.
Note: If the zipper need to be really strong, glue a piece of cloth on the front side too.
Finish off the zipper by cutting a nice rounded edge on the ending with a pair of scissors.