In case your cartesian 3d printer has a longer smooth rod for the Y axis as the frame, and it doesn't have any termination on either ends, this little 3d printable knob might save you some headaches, especially if your printer tends to vibrate a lot.
The bumper is supposed to block the rods from slipping out of the holding frame during the print, and possibly to enlonger the endstop mounting (for Prusa-like builds) point in the back of the printer, and thus enlaring the useful printing area.
The bumper model can be directly put onto a 8mm smooth rod, without further fixing or gluing.
Yet only the 8mm version is available and tested, with PLA printing material.
I am uploading this model in the hope that it will be useful, but without any varranty for the end result, as well as the further usage, and the adventitious damages occuring from it.