Mini Tutorial: How To Shorten A Conventional Closed-End Zipper
If you found a closed-end zipper in the perfect matching color but it is too long for your application, you can easily shorten it at home to the desired length using a few simple steps. The technique described below can only be used with closed end zippers, including invisible and regular zippers with both plastic and metal coils/chain.
1. Starting from the zipper's tope edge measure the new desired length and mark this location directly on the zipper tape using a quilting pencil or tailor's chalk.
2. Thread a hand sewing needle with matching color thread, and using double thread, stitch on top of the closed zipper coils inserting the needle through both portion of the zipper tape. Stitching place a few times, overlapping the stitch as shown above, until the stitch is fully secured.
3. Backstitch a few times on the zipper tape top lock the thread and cut the thread off. Next, cut the bottom portion of the zipper (the portion that is no longer needed) at about 3/4" down from the hand-applied stitch as shown above.
4. The hand whipstitch will serve as an effective bottom stop allowing the zipper to safely open all the way down without risking the slider coming off the tracks.