A callus razor is a tool that is used to remove calluses (corns) from the feet. It is similar to a razor plane, but the blade is usually wider and designed specifically for the skin of the feet.
Calluses develop on the parts of the body where there is pressure and friction. Most often it occurs on the feet and can become painful once it becomes too thick. To prevent this, the callus razor is used to make the feet softer and more supple again.
As a rule, the callus razor is used after showering or bathing, because then the skin is softer, and removal is much easier. It skin is usually carefully dried beforehand, so that tearing of the skin or damage is prevented. Gentle and even application should minimize the risk of skin damage.