no, just use in, but you have to be exposed to the open sky, and fairly in the open. not surrounded by walls or such.
Ok, then that might be why it's not working. I dunno, when I'm in a hostile enviroment I try to hide when I'm going to sleep. I know the game pauses when you are waiting and sleeping but I still want the immersion that I've hidden to sleep.
When I tried to use it I was between a burned out wrecked car and a cliff-face and then the second time I used it I found my way on top of a tunnel and tried to use it. Again, I was between the tunnel top and a cliff-face. I'll try using it more out in the open.
Guess that's why the first one you find is in the middle of a road on an overpass...surrounded by Deathclaws. If you look close at the area you find it there's blood and body parts strewn about. The poor sap was sleeping in the open and got eaten.