This design solves all the basic necessities:
- Fits wooden bars
- Can easily hold the weight of 1+ kg spools
- Fits between the spools
- Can be placed anywhere on the bars without limiting the printers you can use

In addition to above criteria, I've optimized for:

- Customizability: Edit the shape of the brace to fit anywhere you want it to fit, you don't need to re-print the entire guide, just the brace!

- Print quality: Friction-less rolling is achieved by adding bearings, no pulling required by extruder stepper motor

- Economic design: I've added holes in the guide to reduce material use and shorten print time without compromising strength. Since the guide has the longest printing time, I separated the guide from the brace. Just print multiple braces, and move the brace to the desired spot.

- Ease of use: Just place the guide in the bracket, hang the spool on the guide, and off you go. If there happens to be another guide right next to the one you want to use, you needn't move it out of the way. You can place the spool on top of two guides.

- Ease of printing: All objects are placed in such an orientation that requires the least amount of support, has the least amount of friction when using the holder and still get really strong parts!

This brace is made to fit around a 3/4"x 1.5", I will add braces for other 3D printers over time. Check the updates below to see if your printer if supported. Isn't it supported? Ask me! I will always try to reply and make you a brace.

To complete Filler, you will also need two 608 bearings (can also be found in old skateboard/longboard wheels):

- Amazon US: https://amzn.to/2LOilNd

- Amazon International: https://amzn.to/2LQmdNB

Check out Filler on Thingiverse for frequent updates and more supported printers!

https://www.thingiverse.com/thing:3020026

Watch Filler roll!:

Single roller: https://imgur.com/a/RCBPE0M

Double roller: https://imgur.com/a/TVyCf5T

UPDATE (27/07/2018)
Added brace for Prusa i3 Mk2 & Mk3
Added brace for Anet A8

UPDATE (31/7/2018)
Added wall mount

If you have any remarks, please leave them in the comments!

Please do not claim my model as your own or sell it :)

Hugo Groeneveld

Hugo Groeneveld