The 2109 slide comes with height adjustable brackets that fix to the underside of the desk. Optional clip on brackets (633xx) can also be used to bottom mount the slide to the shelf. Alternatively, the drawer member could simply be screw fixed to the side of the keyboard shelf.
There are three versions; EGTRAY-201, CBERGO-TRAY200 and CBERGOTRAY-300.
The height adjustable arm is fitted to the underside of the desk on a guide track. This allows the whole system to be retracted when not in use and then slid out and placed at the correct height and tilt for the user.