Shelves are used to mount other components on. So far, Leaf has three.
The lower shelf is used to hold the microcontroller and associated parts. It is built by placing a 3/4" x 3/4" angle (.055 thickness) across the front and the rear of the frame. I then used a 6 mm thick piece of Sintra plastic to form the shelf. 6-32 screws and nuts were used to attach the angles to the frame and to attach the shelf to the angles.
The angles and shelf were cut to a 12 3/4 inch length. This leaves 1/2 inch in each corner to run wires up and down inside the vertical angles.
The top shelf (on top of the frame) is a piece of aluminum attached to the frame with screws. It is a convenient place to mount the camera microphone and speaker until I figure out something better to do for them.
Lastly, there is another shelf mounted behind the laptop. This shelf currently holds a USB hub and the CMPS03 compass.
Note that there is an aluminum enclosure attached underneath each shelf which provides a nice hiding place for all the excess wire lengths of the USB cables, microphone and speaker wires and laptop recharging wire.