If you do a lot of heavy pulling or a lot of kettlebell work you're bound to have a build up of excess callous on the hands. Excess callous, no matter how good your technique is and especially if you're pushing volume and intensity, is bound to rip at some point. A callous shaver, like the one pictured above, is an investment of less than $5 that can save you training time and energy that might otherwise be lost on needless injury. You can pick one up in the cosmetics section of most department, drug, and even grocery stores.
Unlike a pumice stone that works best after a long bath or shower, a callous shaver is easy to use dry. In fact, there may be a risk of shaving to deep if done immediately after bathing, so take care.