These filament guides are designed to work with the Heavy Duty Printable Filament Spool; http://www.thingiverse.com/thing:10219
They may work with other spools as well.
- Added TOM_Guide_Side_v2 (easier to install)
- Removed original side guide - the new one just works better.
Print them and install as shown in the picture. The bottom guide is important. It ensures that the filament will not come off prematurely and get caught on the spool.
The guides have holes so that you can bolt them in place but I haven't found it to be necessary.