Here is a tutorial that shows how to turn a separating zipper into a closed end zipper.
How to Repair Zippers That Separate or Come Undone — FixnZip®
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Turn a separating zipper into a closed end zipper tutorial
Turn a separating zipper into a closed end zipper tutorial
Create Kids Couture: How to Shorten a Zipper
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Change a Double Zipper to Close in the Centre {tutorial}
Turn a separating zipper into a closed end zipper tutorial
Zipper Rescue Zipper Repair Kits – The Original Zipper