A friend of mine was a Civil Engineer employed by the Port Authority of NY- NJ. Often, as a junior engineer, he worked supervising the PATH Train ( read "subway") repair crews. He told one story about the explicit testing protocol he was supposed to use to insure the 3rd. Rail wasn't energized, before work began. Well in the middle of his test, one of the older workers got impatient and said the equivalent of, " Look kid, here's how it's done." He then stood back a way and threw a metal bladed shovel at the 3rd. Rail. If it doesn't short and send the shovel flying, he said,it's not "Hot".. I'm not recommending that technique to anyone. But, I always found it an amusing story.