Auto jumper cables to verify conduit GND continuity? ;')
Seriously, if you have a 50+ yr. old residential structure, nicely outfitted with EMT indoors (and RIGID outdoors) but good safe GND depends on solid connections all the way back to the main panel, how do you VERIFY that your EMT can actually carry 20AMPS in a worst-case ground fault?
EMT connectors have always seemed a bit lame to me, in terms of CONTACT AREA, and there's all those long runs, hidden behind OLD plaster walls, subjected to who-knows-what kinds of abuse, errant nails, improper anchors, ig-nernt/expeditious "modifications", etc...
So... do you (breaker OFF) disconnect a receptacle neutral at the farthest extent of a conduit run, wire the neutral screw directly to the metal box w/ AWG12 copper, and plug in a 20A angle grinder?... then, while it's running, check voltage drop back at the panel? =:O
Or do you just ASSume it's lame, and pull a new green/bare GND wire?
... what say ye RKIs???