That old boilermaker who showed me how to read a drum head
I was changing out a tube bundle at a paper mill outside Baton Rouge about 4 years ago, and this retired guy walked up who used to work at the same plant. He watched me struggle with a warped channel head for a full hour, then just said, "you're fighting the steel, son, not fitting it." He showed me how to chalk it up and measure the high spots with a straight edge, and we knocked it out in 20 minutes flat. I still carry that chalk trick with me on every job. Anyone else got a random lesson from an old timer that stuck with you more than any formal training?