Makelangelo is a wall hanging, mural drawing machine. There is a motor on the top left and top right of the wall, and belts hang down from there to the pen.
To draw on the ENTIRE wall you need a belt that goes diagonally across the entire wall. That means if the pen were to be in the middle and drop all the way to the bottom it would hit the floor.
When the machine tries to find home by touching limit switches, the pen holder hits the floor as described and then the belts skip off the pulleys.
This bearing holder fits a roller skate bearing (8x22x7) and holds the bearing against the belt, gently pinching it against the pulley. This prevents skipping and allows large machines to find home.
Print one for each bearing, then fit them onto the corners and enjoy!