With this model you can mount a Din A4 Desk Tray on the ceiling of a shelf for example. You will need to print the part 2 times. You will also need 6 Screws. I used wood screws with a 4mm width and the head is 8mm, Length depends on your application. It's a tight fit at first but after a few hours you can easily loosen the desk tray and mount it again without removing the screws.