To regulate the tension by providing a notch or a projected part in a zone of a mount on a rail for the positive positioning of the mount for a guide component and only moving the mount on the rail.

A rail 10 of C-shaped section is provided with an intermediate part 102 and a leg part 104, and mounted on a bay ceiling or a garage ceiling. Projected parts 20, 30 are provided with intervals in the longitudinal direction and in the vertical direction of the rail 10. The intermediate part 102 is directed toward the ceiling and a guide roller mount, a drive device, and a catch are received by the C-shaped section. The mount is provided with the notch in the circumferential direction, and the projected parts 20, 30 of the rail 10 are engaged with the notch. When the tension to a component of the drive device is changed, or the component is changed, the component is pulled from the projected parts 20, 30 at the present position to the other series of projected parts 20, 30, and engaged to enable sure connection.