Well, looks like someone around here has been super fired up by her previous cobbling success - so much so that I've decided to double down and try my hand at a different kind of shoe repair. And so, may I present to you the worn out elastic hall of shame, in which sad, broken down strands of what was ostensibly formerly a piece of stretchy material are now just desperately clinging to the buckles of a pair of sandals:
The trusty tools are much the same as last time (seam ripper, curved needle, waxed thread), with the addition of a piece of elastic of matching color and width (long enough for both shoes). Missing from this picture is tacky glue and a binder clip, both of which are necessary, but both of which somehow missed the mandatory photo shoot. Late night out with the hot glue gun, I guess.
The first thing to do is very carefully seam rip the stitches that keep the elastic sandwiched between the layers of leather. I tried to cut as little thread as I could - just enough to ease the elastic out. The elastic appears to have been glued as well as stitched into place, which is probably why it was still somewhat attached to the shoe strap.
Fold your replacement elastic in half, and then cut it to be just slightly shorter than the old stretched out one. You don't want it too loose - instead, you want the stretch to engage a little bit when you have the shoe on.
The next thing is sort of jazzy and improvisational (or at least I couldn't figure out any sort of methodical approach to doing this). Slip the bar of the buckle through the middle of the new elastic, trying not to break any of the threads or rubber by kind of just pushing them all apart and shoving the bar in between.
Now it's time to re-assemble the thing. Get out your favorite fabric glue (I like Tacky Glue for its... well... tackiness) and smoosh a bead on the inside of the leather. If the leather is the bread of the leather-and-elastic sandwich, then the glue is the mayo that holds it all together.
Slide the elastic into place and clamp the whole thing closed with a large binder clip, or something similar. The key is to position it so that you can still access some of the seam, because that's what you're about to start working on.
Tuck the thread knot into the sandwich and start sewing along the side that you've left out of the clip. The easiest thing to do is just use the same holes that the old stitches used. Make sure, as you sew, to push the needle through not just the leather "bread", but also through the elastic. That way it'll really be anchored in there. As you go, keep repositioning the binder clip until you don't need it any more.
And voila! You are done. Now fix up the other shoe to match, and you are off to the races!