this was in Flaint Michigan in the early mid 60’s
this was way back before much of anything was automated...and I spent all day BENT OVER walking along the line following a moving truck installing heater vents .......etc..into the cabs...
very unpleasant...physically and very draining..
I had very little patience or anything else left by the end of the day.
I was told to slow down...by guys who were “union members” .several times a day during my “tenure” there.