Back in the days there used to be this thing on top of the drawing board that we called a a tracer because it could be folded out and used to trace the outlines of f.i. a drawn object you wanted to copy.
I have tried to find it on the net, but the closest I could get was this: https://en.wikipedia.org/wiki/Drafting_machine which is more or less the same thing, but a lot bigger.


Xiste