UPDATE! I'm pleased to see the positive attention this little part has gotten. I've added a version that has the belt clamps (for GT2 belts) built in, which has a couple small benefits. You can modify the scad to make something similar for your belts. Or I can help you out if you leave a note. (6/8/2013) I'm using Greg Frost's excellent X-Carriage on my Prusa Mendel reprap. I was a bit frustrated, though, that I couldn't find any designs here to mount a fan behind the x-carriage. So I made this, and I've had much success with it. For me, at least, this allows the fan to be closer to the print head than if it were mounted on the sides, and it saves a non-trivial amount of x-axis print space. If you futz with this design, and I hope you do, please let me know what you come up with. I leave as exercise for the reader the creation of built-in belt clamps, fan ducts, fan brackets, and the like.