Diesel mechanic: get a job in a place where you don't feel like you need to carry while working on the trucks/boats. A gun is going to get in the way guaranteed. I work on my cars as a hobby and no matter where I carried it a gun would wind up getting in the way if I were to try and keep that thang on me while wrenching.
Climber: What benefit do you see to climbing radio towers with a gun on you? Leave it in your truck. There are no nignogs sleeping off fent on radio towers and you're not going to keep it ready while climbing down a ladder if someone is waiting at the base to rob you.
This whole discussion is kind of silly, carrying on the job in many trades just isn't feasible because it will either get in the way or wind up exposed. Most tradesmen are always having to contort themselves into weird positions that would reveal a gun if carrying, whether AIWB, 4:00, ankle, whatever, plus leaning on stuff or crawling around. Basically pocket carry of a small gun is the only realistic option imo and even then leaning on a truck frame with a gun in your pocket while you torque a bolt sounds really comfortable. Maybe fanny pack/body bag carry. I carry all of the time, I considered FFDO, I get it. But sometimes it's just not practical.