The structure of the sole is quite complex. In a broad sense, it can include all the materials that make up the bottom, such as the outsole, the midsole and the heel. In a narrow sense, it only refers to the outsole. Generally speaking, the common characteristics of sole materials should be wear-resistant, water-resistant, oil-resistant, heat-resistant, pressure resistant, impact resistant, elastic, easy to fit the foot type, not easy to change after setting, heat preservation, easy to absorb moisture, etc. at the same time, it should cooperate with the midsole, and have the brake function when walking to change the foot, not causing slipping and easy to stop, etc. There are many kinds of sole materials, which can be divided into natural and synthetic ones. Natural base materials include natural base leather, bamboo, wood, etc., while synthetic base materials include rubber, plastic, rubber plastic composite materials, recycled leather, elastic cardboard.