Truck camper checklist and supplement to owner's manual

I have a question also if you turn off your propane tanks then why do you also turn the selector to the middle? I leave it on the tank that I'm using then I know I'm using my low tank and I don't have to remember which tank I was using prior to leaving.

I always try to use the outside tank in the compartment first. When I think I'm getting glow I'll find a place that fills by the gallon and not the tank and refill it.