YOUR MISS MANNERS QUESTION OF THE DAY: Is it more polite to knock on a bathroom door, or test the doorknob to see if it's locked or not? Testing the doorknob at first seems to be the ruder action--you're jarring somebody in the midst of a private bodily function. Yet, if you knock, you're putting the burden on somebody to respond to you. And who likes talking to anyone in the midst of a good number two? Not me, that's for darn sure. Testing the doorknob answers the question "Is this bathroom occupied or not?" in a quiet, efficient manner, and may be, in the final analysis, the best action. Of course, this depends on the assumption that everyone locks the door to the bathroom when they go in--and they bloody well should--but if that assumption does not valid there will be problems, to put it mildly.
Testing the doorknob and THEN knocking and asking "Hello?"--because you didn't like the answer you got from just rattling the doorknob--is, of course, completely idiotic.
1 hour ago