This is a spool holder for storing your cable, solder, etc. spools in as small space as possible.
There are two wide slots at the front for unwinding the wire either from the top or bottom depending on your preference. The middle hole is for stowing away the wire when not in use.
Holes in the rollers and an optional crank handle make it possible to wind cables from spools that are of wrong dimensions to fit inside a 1x1 Gridfinity slot.
The rollers use two 608 ball bearings for that smooth rolling action 👌. You might be able to cobble something together in CAD if you don't have spare ball bearings / don't care so much if the mechanism rolls very smoothly or not.
Printing & assembly instructions:
I used PLA, 0.20 mm layer height, 0.4mm nozzle. No supports or brims are needed.
Print either the 1x1x1 or 1x2x2 spool holders. The smaller one can fit spools of up to 34mm diameter and the larger one up to 74mm diameter.
I recommend securing the holders to weighted baseplates with magnets.
Print one of the spool rollers depending on your spool's inner diameter. There's a version specifically for winding, which has a core diameter that's as small as possible (to fit as much wire as possible).
Attach one 608 ball bearing per half.
Note that on smaller diameters the chamfers are quite large (so that the model doesn't fall apart due to the ball bearing slots), which limits how wide your spool can be. The chamfers also help with ease of printing. This could maybe be remedied somewhat by tweaking the model and / or print orientation.
Print one roller screw, thread it into the spool roller halves tightly. Optionally insert a spool between the halves before attaching them together.
Gently push the roller assembly down into the spool holder.
If you're going to wind the spool, either use a flathead screwdriver (or electric screwdriver if feeling adventurous), or print the crank handle. The two crank handle parts require quite a bit of force to attach, I squeezed them together using large pliers.