You said you learned to knock on the wall and listen, but isn't the real lesson to verify the room itself first? A hollow sound just tells you it's not an exterior wall. I've seen guys knock, hear it's hollow, and still cut into the wrong room because they were in the wrong unit. Always check the room number or a permanent landmark, like which way the hallway runs, before you even pull out a tape.

What did you expect from mud called 'FeatherFinish' in an oven?

Yeah, a good editor can absolutely fly through pages.