Without a stabilizing cross joint in its back a shelf will be shaky and can easily lose balance. As a result a rhomboid movement is made possible and the shelf tilts to the side.
The created overhang can be used for new purposes. A mixture of pivotal points and firm connections enables some of the shelves to keep their horizontal position while others follow the tilting movement. In the upright position the overlapping shelves serve as chutes for papers and magazines. When tilting these elements swing into the horizontal whereas their counterparts tilt into the angle and form a sloping tray for books. The rotary bedded shelves stay horizontal in any position.