RAK has a Unify enclosure with screw sites on the back. This tab lets you screw it to a flat surface. I used 12mm M3 allen heads, but perhaps an improvement would be to use flathead screws and modify the holes so the heads are flush.

Specs for the Unify enclosure here: https://docs.rakwireless.com/Product-Categories/WisBlock/RAKBox-UO100x75x38-Solar/Datasheet/