A human powered vehicle uses human power to propel the vehicle into motion. They can be propelled by the person in the vehicle, or by the person outside and not supported by the vehicle. Rolling contact, sliding contact, intermittent contact, no contact, or a combination of the four is used to support the weight of a human powered vehicle. The bicycle is the most common, and other wheeled versions include inline skates, strollers, rickshaws, skateboards, and wheelchairs. Vehicles with sliding contact are skis, snowboards, and sleds, and those with intermittent contact include stilts and pogo sticks. A gurney or stretcher is a vehicle that requires no contact. Drivetrain, lateral motion, or direct contact with the ground, are the three types of propulsion that drive the vehicle.