In the matter of salesmen, it goes like this:

Supervisor: "What did they say at X house?"

Salesman: "I didn't knock, they had a notice saying 'no salesmen'."

Supervisor: "So fucking what? You knock on the door, you wait until someone answers, and you go through your script, never mind any bloody notices! Do that again and you're fired!"

Poor buggers are between a rock and a hard place.