we had a darkroom with 4 exposure units for adding line screens in 4 color process jobs.
I had the Magic slate account ( where you draw with a plastic pencil and then pick up the flap and it's gone) I had to hand cut rubylith for all of those and then add the screens in for the other colors as they only used CMYK to print.
The best part was walking in and scaring the Pooo out of people :D