This is a cable management piece for the Hummie deck. These holes fit the unity power switch and standard 5.5×2.1 mm waterproof charge port. This is meant to combine with the Hummie deck riser V2 (https://www.thingiverse.com/thing:3777916). The charge port bolt is close enough to the shelled wall that it doesn't want to turn. Instead, screw the charge port into the bolt while it's already in position. I recommend silicone or at least hot glueing the inside when assembled for water proofing.
Inland PETG, PLA, whatever