Do you know where the SAM missile vehicle is in the warehouse? Go up to the window overlooking the other warehouse by the minivan and bulldozer. Look straight at the dumpster you can see out that window. Next to it there is a small opening and you can go
in an approximately 4 ft by 4 ft storage shed/box/room thing. Like KO said there is literally no use for it because if any explosive gets in there it's an instant death. Personally, I prefer the sleeping bags and campfire spot better.