|I have found an aid in shortening jeans zippers. I could just install them and let the top fall where it will and cut off the excess, but I like to put at least one stop at the top. It looks and works more nicely.
I use nippers to pull the teeth off the area where I will shorten. I mark where the zipper will end and remove the teeth, plus a couple extra where I will replace the stop. I use the nipper to open the top stop. Previously, when I squeeze nippers to reapply the zipper top stop, sometimes it will jump and maybe I will or maybe I won't find it again on my floor. Very frustrating to spend time on my hands and knees looking for the little bugger.
I have been using this 1/4" leather tape for all kinds of things. But I think I like this use best. (The leather tape is a double-sided tape used for hemming leather. It is MUCH stickier than the normal double-sided sewing tape. CAUTION- if marking a placement, say, a patch, don't put where your needle will go through it. It gums up the needle something fierce!)
I cut off about 1/8" of the tape and apply where the stop will go, placing it so you can wrap the zipper tape. Take the backing off and wrap. Stop crimped on over tape No more leaping zipper stops!
Another pic of nippers