The items of footwear worn while playing football are calle football boots in British English. They feature studs (cleats) protruding from the sole for traction on a playing field covered with grass or similar surface; hence they are called "cleats" in American English. Association football boots are called soccer shoes in American English. In most codes of football, modern "boots" are not technically boots as they do not cover the ankle. They can be made from a wide variety of leathers, kangaroo leather being a popular choice.