When I did Technical Drawing as a spotty yoof (Grade 4 CSE) my teacher used to say that in a professional drawing office they would use electric rubbers, I've just googled & they are actually a Real Thing ....
For erasing ink lines drawn on tracing paper, you needed them! A chunky line drawn with a Rotring pen, with its ink so dense I'm convinced one drop could turn the worlds oceans grey, does take quite a bit of shifting.
Our drawing office in which I worked had one, but excess use of it didn't go unnoticed... Sometimes you were carrying out legitimate amending of a design, but at other times it was 'cos you'd screwed up. A bit easier in CAD, where its select, then hit the delete key, and its gone cleanly.
After getting thrown out of Art Skool I scored some employment as a technical illustrator at the big Maxwell house up on Headington Hill in Oxford in the drawing office at Pergamon Press. Said 'office' housed at least a dozen wonderful heavy weighted fetishistic parallel motion drawing boards and high stools. New recruits like myself sat at the back of the room. As one 'progressed' through service or more importantly, productivity, we moved towards the front, which was glass fronted and overlooked Oxford's manifold spires. I progressed rather quickly to the annoyance of several old retainer cardiganed pipe smoking duffers and enjoyed monthly bonusses as well as a board at the front
Any road up, all of my 'illustrating' was done in ink via bow pens on thick tracing paper - the method for '
erasing' errors was to scratch the ink off with a scalpel.
I drove an Austin A40 (Farina, Horizon Blue), wore loon pants and took acid at the weekends, sometimes up Wittenham Clumps at dawn
ps thanks to this thread I've ordered Brucey's Pentel recommendation
