Recently, I stuffed a woven-polypropylene bag a mite too full of stuff and managed to pop the its zipper slider (the thing with two nostril-like orifices which one pulls back and forth) off one side of the zipper’s “chain” (the teeth that get drawn together or separated when you zip or unzip a zipper closure).
The Components subsection of the Wikipedia article on zippers features a labelled diagram of a zipper.
We have other similar bags and I used them, setting aside the one with the zipper I’d forked up to either fix or discard.
When I turned the bag inside-out and looked at the zipper from the inside, I saw that there were no metal “stops” (i.e. no pair of metal pieces, one on either side of the chain, and no one metal piece joining the two sides of the chain to keep the slider from leaving the chain) at the nearest ends of the zipper tape. All that had prevented the pull from leaving the teeth (at that end, anyway) had been the barrier provided by the woven polypropylene fabric of the bag. On the inside of the bag, a few stitches held the zipper tapes together.
I snipped those bits of gray thread, fed the slider back onto the teeth of the chain with the zipper pull facing up and then stitched the bottom of the tape back together, but taking the threadthrough the woven-PP bag fabric as well this time. For the heck of it, I used orange aramid 1313 sewing thread, doubled up (each stitch is four threads instead of the usual two) and made some of the stitches wide to try to ensure they wouldn’t pull through the rough (i.e. relatively thick-fibered) PP fabric.