So I have this callus on my right big toe that I never felt or noticed until relatively recently. That put in mind calluses that were on my thumb and ring finger from high school, when I used a pencil for hours a day; both are since healed in these days of keyboards.
It did make me wonder, though (and make any assumptions you want about my imagination from this; it’ll probably be at least 25% true): suppose a sadistic mad scientist invents a device that, when a person is inserted into it, rubs that person’s skin constantly, all over their body, in a way that, on a single part, would eventually create a callus. Would such a theoretical unfortunate’s entire body be callused?