Easy. If you get shocked, it's 120V. If you get killed, it's 220V.

I tend to build wheels without either, I balance tensions by plucking spokes. My old co-op has a tension meter, and I've checked tensions I've set by plucking, and I'm usually able to get them pretty close. I still go back there when I need to build wheels, all I use is their Park Tools truing stand and 4-sided Park Tools spoke keys. I have an old spoke for fitting spoke nipples, it's bent into a sort of T-shape so I can grip it better, but I never remember to bring it

I encountered a fixie once where the owner was complaining about a rattle. I found a spoke nipple in the deep V-section rim on the front wheel. It'd been in there for months...


I know two people who've survived shocks from the 240V mains we use over here. Admittedly, one of them flew about 5 feet backwards and the other one doesn't remember it well enough to say how far he went, but still...