This design solves all the basic necessities:

• Fits almost every object with a flat top surface and printer frame when customized.
• Can easily hold the weight of 1+ kg spools.
• Fits between other spools if necessary.

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

• 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!

Currently the following braces are available:

• 3''x4'' beam
• Wall mount
• Stand
• Prusa i3 Mk2/3
• CR-10/Ender 3
• Creality-included arm
• Anet A8
• Ultimaker

Other braces can be found in the remix section (or on Thingiverse!)

To complete Filler, you will also need two 608 bearings (can also be found in old skateboard/longboard wheels). For those who find that Filler has too little friction or do not have 608 bearing available, I've also designed plastic bearings to combat these problems:

- Amazon US: https://www.amazon.com/Skateboard-Bearings-Double-Shielded-Silver/dp/B002BBGTK6/ref=sr\_1\_8?ie=UTF8&qid=1532522237&sr=8-8&keywords=608+bearings

- Amazon International: https://www.amazon.com/Skateboard-Bearings-Double-Shielded-Silver/dp/B002BBGTK6/ref=sr\_1\_8?ie=UTF8&qid=1532522237&sr=8-8&keywords=608+bearings