The look of corns on the hands:

The lesions are round or oval limited keratosis, the size of a pinhead to a broad bean, yellowish or dark yellow, the surface is smooth and the skin flat or slightly elevated, the boundary is clear, the center of the inverted conical keratinous plugs embedded in the dermis.

Because the tip of the keratin plug irritates the nerve endings in the papilla of the dermis, it causes pain when standing or walking. Corns are found in the middle of the front of the metatarsal at the head of the third metatarsal, the tibial edge of the toe, but also in the little toe and the back of the second toe or between the toes and other prominent and friction-prone parts of the foot.

Prevention

To prevent corns from occurring, friction and extrusion should be reduced. Shoes and boots should be soft and fit well, shoes can be lined with thick and soft insoles or sponge pads, cut holes in the equivalent of corns (perforated insoles). Toe deformities should be corrected and treated, and if there is an exophytic bone wart on the foot, it should be treated surgically.

Reference: Baidu Wikipedia - Corns