The MTH hand car won't work on the earthen bumper. I used one of the rubber feet you put on the bottom of a coaster or whatever so you won't scratch a table surface. You can find them at any home improvement store in the hardware Dept. The larger size stick out just enough to activate the reverse. They self stick but will loosen up after a few hits so I just glued mine on. The rubber ones give a little more cushion than just hitting a hard surface.