These are simple covers for a small open space in some storage I use for dry boxes, the space is typically the “handle” as well so the little knobs are caps for M3 round screws.

-High fan speed for the over hangs

-The hollow pillared back piece is to close a gap and minimize the length of the screw, but can also be used to just glue the pieces together, and if you aren't bridging a gap you could just use the front plates!