A robotic device movable in first, second and third mutually perpendicular directions along rails arranged in multiple rows, where the rails in a row are arranged along the first and second mutually perpendicular directions, and the multiple rows are arranged along the third direction perpendicular to the first and second directions. The robotic device has a frame, wheels coupled to the frame for moving the frame along the rails in the first and second directions, and support handles for lifting the frame in the third direction from first rails arranged in a first row of the rails to second rails arranged in a second row of the rails. The support handles are configured for providing engagement with the second rails so as to lift the robotic device in the third direction from the first rails to the second rails.