In the 1980s and presumably before, plugs like this often only had screws you needed a screwdriver to tighten.

I don't know if this was to prevent people disconnecting things, or if the expectation was that once connected, things should stay that way for years.

It helped me a lot when I had a colleague who had a strong workman's hands and who could not be found at the end of presentations where he had set up the projector's cabling.