I'd like to be ready in case someday I have to do an emergency shutoff of my house's nat gas supply. I see on the exterior gas meter an elbow where it comes out of the meter and turns into the house. At this elbow is a square bolt, ~1" sides. I don't see any other likely shut off points.

Is it likely this is the shut off? I assume if needed, a large wrench turning it clockwise would shut down the gas into the house.