Closet Bar Clip
This is a ridiculously simple thing. It is intended to keep things from sliding on a closet rod.
I made this a long time ago, but finally figured I'd put it up in case it could be useful to someone else.
These could be useful in the closet of a motor home or trailer, or maybe for organization in a home closet.
I made this to help feed plastic to my printer. In my basement home-office, I have a closet rod hung up between rafters on which I hang my filament to feed to the printer below. These clips go between the spools to keep them from sliding around or rubbing against each other and creating friction.