For us wot fixed the broken toys, there was "Fred the Wheeltapper" who infamously changed all the wheels on the train and then found out his hammer was cracked. In another poster he taught us to give our instructions clearly and concisely, as he told his hammer wielding assistant - "When I nods me head, hit it."
There were lots of similar 'Human Factors' posters, long before HF was invented: I suppose the fact that we remember them so many years later shows how effective they were.