My wife wanted something screwed to the wall, but then again, she doesn't repair the drywall. So, a counter-top Thing is it. The toothbrushes are just resting there in the open air, so that there is lots of circulation around them. The weight of their batteries keep them in place. The bottom comes a bit forward of the top, keeping the center of gravity such that it will not topple over, even with the toothbrushes in place.
This thing is designed heavy-duty, hence the 5mm walls.