These warts are called plantar warts. Plantar warts tend to grow in a group the size of a quarter or larger. These grouped warts are known as mosaic warts. Most plantar warts do not stick up above the surface as much as hand warts, because sometimes the pressure of the walking on them flattens them and pushes them back into the skin. Often black dots, which are the blood vessels that feed the wart, can be seen.
Plantar warts can be common in people who sweat heavily and who do a lot of walking or exercising.
Flat warts are much smaller and are less rough than hand or foot warts. They can occur anywhere, but in children they are most common on the face. In adults they are most often found in the beard area in men and on the legs in women. Skin irritations from shaving probably account for this. Genital warts have become a more common and worrisome problem in young adults.