Abstract: The invention is a system that is movable along a guide. It includes housing having a center of mass, a first wheel and a second wheel, each connected to the housing and configured to rotate about a respective axis. Each axis is displaced from the center of mass to create a rotating moment that biases the first wheel and second wheels into frictional engagement with the guide. The invention also includes a rotator, and controls in communication with the rotator and positioned at a location remote from the housing. The housing moves relative the guide.