Re: Watch this!
Worked at British Telecom back in '87, doing exchange maintenance. The exchanges had massive interleaved busbars for the 50V DC supply running above the racks, + were copper with insulation, - were aluminium uninsulated (IIRC).
Smaller strips down the height of the rack, with threaded holes every inch or so. To hook up a new unit to supply, poke a hole through the insulation on the +ive, then just screw on terminals. One day my mate Ron was doing just that, using a cable lacing tool that looked like the eye of a really big darning needle mounted on a wooden handle. I saw a bright flash and heard a 'crack!', looked over to see Ron, hand shaking, holding a truncated cable lacer... he'd pushed through a bit too hard, chipped some metal from the rack frame and shorted it. Neat puddle of metal on the floor.
My line manager also had a neat circular scar around his ring finger where his wedding ring used to be...