What should I do if I put up a sign at the door and knock at the door?

Communicate with the knocker to explain the reason and ask the other person to apologize. If a sign is posted at the door and the opposite person is still knocking at the door, you can open the door, communicate with him, explain the reason, seek the understanding of the other party, point out that the sign is posted at the door, and finally ask the other party to apologize. This is the solution.