Y axis bumper

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.