After mounting a spool holder to the front of a Makerbot Replicator 2, I wanted a bracket for the filament guide tube that would also mount on the front of the printer. This bracket mounts to the front of the MR2 using the existing center bolt. 

The two side-by-side holes that run perpendicular to the filament are meant for short sections of rope, pipe-cleaner, rolled up cloth, etc. This material should remove any dust or particulates on the filament and prevent future nozzle jams. Once the filament is threaded into the filament guide, you can push it between the cleaning material into the bracket: the bracket does not need to be threaded onto the filament. 

There are STL's with a few different hole sizes for the cleaning material, to fit whatever diameter rope,etc you have on hand.