This is designed to fit over a Tetrix axle or motor hub. We designed it to feed a string from one side while reeling it in on the other. Print it standing up with supports (in the holes as well as to the plate) for best results. You can get by with just the stands running to the plate, but the hole where you insert the hub may not end up circular.

Pay attention as you insert the hub to make sure the set screw is towards the hole inside the spool. That lets you tighten it up with the hub completely hidden inside the spool.