The owner of a 70' trawler under construction "borrowed" my 1/2" Snap-On" combination wrench and shorted it out against the hull. Trouble was there were 8 8-volt batteries (32 volt system). The wrench instantly turned white hot after a blue flash. It burned a huge hole through a 5/16" steel hull.
"You owe me a wrench John"
"No way. And how much is it going to cost to repair three melted terminals on my new batteries, and the wiring?"
"A hun-- I mean, three hundred dollars" (this was thirty years ago).
He "knew-it-all" "I-don't-gotta-disconnect no stinking ground cables"
"Ignore" and "Ignorance" are two closely related words...