Steam era signals

[Lester Perry]

I have watched switching operations for the last 20 years and the brakeman uses a radio to communicate with the engineer. But what about in steam era? I only know of one practice of how an engineer knew when he was clear a crossing on a main line. He knew how many cars he had and knew land marks for train length. But what about in a yard or spotting a car in a curved track? Someone had to say stop some way when vision is blocked.