A 20mm (+ intolerance) plug to cover for example those square cable shafts you have on your Makerbot. My main motivation was to keep those bits of plastic from the wipe procedure and loose nuts and tools from falling down into the hardware compartment. Plus they do look nice and tidy.
Print, let the plastic harden out, plug.
Print, harden, thread wires through cable shaft, plug.
The stl files come in two versions which work for me and PLA: With and without cable shaft. They have an actual size of 20.6mm. These should fit tightly in the holes, as the cables will exert force when moving up and down. If they don't fit, edit the scad file.