which wall's on first?

I had just checked in a middle-aged lady and sent her up to her room when a gentleman came in needing a room. As I was checking him in, the phone rang. It was the woman I’d just checked in. Uh-oh.

Schatzi: Front desk, how can I help you, ma’am?
Guest #1: Where’s the air conditioning unit in my room?
Schatzi: Well, it’s in one of two places, ma’am: the front wall or the back wall of the room.
Guest #1: Which one is that?
Schatzi: The front or the back?
Guest #1: Which one is the front wall?
Schatzi, flabbergasted: Which one is the front wall? The one with the door in it.
Guest #2, who I’m checking in, sotto voce: “Which one is the front?” You’ve got to be fucking kidding me!
Guest #1: I don’t see that.
Schatzi: The door through which you walked into the room—that’s the front wall, ma’am. The back wall is directly opposite that.
Guest #2: Is she fucking retarded?!?
Guest #1: I don’t see an air conditioner there.
Schatzi, cheerfully: Then it must be on the back wall!
Guest #1: All I see there are two beds.
Schatzi: That’s the side wall, ma’am. The back wall is across the room from the door.
Guest #2: [various profanities]
Guest #1: The tv is there.
Schatzi: No, ma’am, that’s the other side wall, across from the beds. If you put the phone down and stand in the doorway, then walk all the way across the room, you should find the air conditioner on the wall. I’ll wait on the line while you look.
Guest #2, who I’ve finished checking in: I’ve got to see how this turns out.
Guest #1, after a wait: I found it. [click]
Schatzi to Guest #2: Not even a “thank you!”
Guest #2, shaking his head: I can’t fucking believe some people.

Unfortunately, I can!