Here's one of the weird things Parkour brought to my life: a callus shaver. At first, I was all proud of the thick calluses building up on my hands from all the QMs and climbing, thinking that the thicker they were, the better my hands would cope with various surfaces.
Until one of them broke off.
After cleaning up the embarrassing amounts of blood and waiting for the hole in my hand to heal, I started shaving my calluses religiously. A callus shaver is basically a bent razor blade on a stick, and you gently scrape the hardened skin off with it. The most usual spot for calluses is the place you grip things with at the base of the digits. With time, they also appear at the base of the palm (heel of the hand), on a straight line around the middle (lower part of the ball of the hand), and along the first phalanges. So far. I end up shaving the larger ones 2-3 times a month, the smaller ones on occasion, whenever I start feeling them while exercising. It's kind of a weird habit, but it beats having bloody gashes in your hand anytime!!