US Patent 7243926 Runner sled that is twistable during steering

A sled includes a pair of runners that are formed from a single, continuous, hollow plastic pipe. The runners are fixed to a platform at three locations: the rear ends of the runners curve upward and are attached to the rear end of the seat, while intermediate portions of the runners are attached to downwardly extending legs of the seat. The forward ends of the runners curve upward and support a footrest via retainers. The seat and the footrest are connected together by a rope. The runners are twistable during a steering operation.