Welcome to a new feature where I ask our own Jason Torchinsky to answer random questions — from readers, people I meet on the streets, and imaginary folks he thinks he's talking to — in handy flowchart form. We call it "Flow on the Floor." Today he's answering: Should I bother knocking? — Ed.

You'd be amazed how often this question comes up. Some vans provide the answer in a handy placard affixed to the vehicle, but in other cases, this flow chart will provide you with the proper etiquette guidance.