Skiing is a sport that is accomplished on long thin boards or facsimiles made from other materials that are attached to the feet for locomotion on the snow. It is accomplished on steep inclines (downhill or alpine), flat ground (cross country) or in the performance of stunts or tricks (freestyle). The skis are waxed to make them slippery for alpine and freestyle skiing and to grip the snow in cross country to provide thrust. The skier will often use hand held “poles” to assist with balance and thrust during the activity. Skiing can be done on commercially maintained slopes or trails as well as unmarked natural snow.