Invisible zipper foot
This is a presser foot for sewing invisible zippers. I found that to get the best zipper I had to stitch it once, relaxed, then again pulling against the zipper a little to make sure it opens up the zipper and allows the needle into the little crevice (look up how to sew an invisible zipper.) You could probably do it all in one go, but for me, it was easier in two. For the shaft I had a piece of one of those big black paper clips that had broken. I think it would be a little happier with a slightly larger one. The last picture is the zipper I sewed with it, partially unzipped.
This is my first design, and the second thing I printed (print quality isn't that great in the pics).
This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/iCVpkCh8mLu