Plots tilled by oxen were long and narrow since ox teams were so hard to turn. Medieval farming practices used the open-field system, in which serfs were given thin strips of land, conducive to ox teams. When horse collars were invented, horses could pull more weight and maneuver better, leading to more variable shapes of fields. When serfs were freed and became independent farmers, they sought out horses, which had other benefits (see Horses, peasant mobility and urbanization) and eventually the open-field system faded, except in more backwards places like Russia, where the system dominated until the revolution.