Just a simple clip on spool holder for a wire rack. Secure to the rack using zip ties for best results. I built it to organize shrink tube, abrasive sleeve, and wire on a rolling rack for my technicians, but it can also be used to organize filament spools.

For the rod I used thin wall ½" steel tube I bought at the local steel yard. very cheap and plenty strong for the application. I drilled a ¼" hole in the end and put a cotter pin through on the outside to secure the tube.