Everyone knew not to use our front door. It was for people we didn’t know or didn’t like; like the Jehovah’s Witness.
Our garage door was the one used by most people and the familiar banging of the screen door as it rattled in its frame could tell us exactly who it was. By this I mean that the intensity and the duration of the knock allowed us to determine whether we wanted to answer it or not.
Very few people came around to the back door. Only special people and long term friends knew that it was okay to do that.
I guess in a way it was like anal sex. You didn’t let just anyone try. You needed to build up to that and have a trusting and long-term relationship.