Tech training movies... I remember seeing one at Halton that must have been made in the 40s. It was to demonstrate the venturi effect and consisted of a flight of apprentices (in hairy best blues) marching along towards a collection of tables arranged as a venturi. When they got to the said tables they then had to double through them and relax back into march having exited the other end.
The film was obviously effective because I've never forgotten it after thirty-odd years.
