A1 movement prevention

My A1 started to move around on the shelf after some time, probably in combination with worn legs and small dirt. This ruined a few prints, but what's worse, it would have risked falling off the shelf to the ground, which would probably mean the death of the printer. So I decided to draw these securing devices and screw them to the shelf. It's not rocket science, but maybe it will save someone some time. Let it print :-)