A trick the shop monitors used to deter "casual" use of our old 40s era South Bend benchtop lathes was to pull the knob behind the chuck that engages the back-gear, but leave the shifter on regular....so both ratios would be engaged simultaneously, locking the chuck through the transmission. It was kind of a ruse, technically nobody was supposed to use them after hours when the monitors went home, but it was kind of seen that if you knew enough to figure out their trick, you probably knew how to use it in the first place. It was also possible to get the backgear shifter in between the two positions, giving a false neutral.
Most people who didn't take the basic machine tech class were too baffled by the old south bends to use them anyway. They're of course purely mechanical, had have probably a dozen shifters, knobs, and selectors. None of them labeled or obvious as to function. There's a certain mechanical elegance to running such old machines. Gentle whirr of countless gears all spinning in precise concert, just don't get it from newer or cnc machines.
