
The two screws at the bottom center of the circuit board is the power
and ground connectors (left to right).
The side with the fuses (left side) is the power (+) and the right side
is the ground (-)

The bottom of the tool tray with the 4 screw showing through.
You can put silicone sealant to water proof the 4 holes.

The stainless steel cover on the unit but the cover is not screwed down.