This is a solid, firm case for Waveshare 7" USB+HDMI LCD displays. I didn't like the one the screen comes with, it just doesn't seem solid enough for one to safely transport the screen. This one surely is.
The case have two cavities on bottom and top walls - one may design a snap-in front cover if there's such a need.
Supports are needed mostly for nuts and screw heads. Use M3x15 screws + M3 nuts to assemble the whole thing.
If you want to put the screen on the flat surface, I include low and high stands for the screen (remember to print at least two).
There is a number of mount holes on the back of the cover. You can either mount Raspberry 3B (M2.5 holes matching Raspbbery board), mount one of Raspberry covers (see photos, either you can screw on one to another or leave screw heads hanging to hang the cover - as I did) or design your own Raspberry case - there are M3 holes horizontally distant from Raspberry board holes by 1 cm.
If you need a different mount or you want to remove the holes altogether, I include the complete Fusion 360 archive file - happy designing :)