This is meant to be a stationary node, not a portable handheld device. It features:
The mounting system on the back of the case consists of four holes in a 100mmx70mm square and two holes in the center spaced 40mm apart (see picture). These holes do not go all the way into the case, so water can't leak through them. They are sized for M3x4.6x6mm heat set inserts.
Parts list:
Note that this case is weatherproof, not waterproof, even with a TPU seal. I stuck it in my shower directly in the water stream for like an hour and it was still done dry, so rain isn't gonna hurt it. However, when I submerged it overnight (without the electronics inside obviously) it filled about halfway with water, so there was a small leak somewhere. There's a small hole in the bottom of the case which you can either leave open to act as a drainage hole in case some water does get in, or you can seal it with an M3 bolt.
The author remixed this model.
Rugged Box (Parametric) by Whity is used as the base, obviously very heavily modified.