A skateboar is a four wheeled platform used for the activity of skateboarding. It is propelled by pushing with one foot while the other remains on the board, or by pumping in structures such as a mega ramp, vert ramp, half-pipe, mini ramp, quarter pipe or bowl. A skateboard can also be used by simply standing on the deck while on a downward slope and allowing gravity to propel the board and rider. That having been said, the skateboard cannot be concisely defined. Unlike most other sports, yet not unlike most other modes of transportation, not withstanding motor vehicles and select other modes of travel as well, there is no governing body which declares any regulations on what constitutes a skateboard or the parts from which it is assembled. For example, longboards are a type of skateboard with a longer wheelbase, and are typically proud owners of larger and softer wheels. Thus, the definition of a skateboard can vary in shape, size, overall appearance, as well as in aptitude for performance.