The heel height is usually 7 inches (18 centimetres) or more, depending on the size of the shoe. This heel is as long as possible, so that the wearer's foot (ankle and toes) are fully pointed/extended in the shoe; any longer would prohibit standing or would require a platform. The boots may rise to any height on the leg, but most designs stop at about the ankle or the knee. They are often laced up the front so that they may be made as tight as possible. The knee-high and thigh-high versions may also have zippers (zips) to allow them to be donned and doffed more easily. The thigh-high versions may be designed to stop the leg being bent at the knee, further restricting mobility . There are also dozens of "ballet shoe" designs, including sandals, mules, and Mary Janes, many of which have buck