The invention is a cube with a flat top and bottom. Both the top and bottom are covered with a partially sunken rubber or silicone layer. The height of the cube varies from 20 mm. to 40 mm whereby one side at the bottom is always longer than the other sides, up to a maximum of 10 mm. These cubes can be placed on the side of a plate or a flat object after which another plate or flat object can be put on top of the cubes. For stability a minimum of three cubes are necessary.
