Abstract: A first free line composed of two rails arranged in parallel in a substantially horizontal plane is joined to a second free line composed of two rails arranged in parallel in the substantially horizontal plane. A switch rail pivotally movable in the substantially horizontal plane is provided at each of the junctions where the rails of the first free line are joined to the rails of the second free line in corresponding relation. Another switch rail pivotally movable in the substantially horizontal plane is provided at a cutout portion formed in the intersection of one of the first free line rails with one of the second free line rails.