It used double tracks for glass roof. It is not only designed as plane, arc, but also round skylight blinds. The requirement of strength of this style is rather low. It is light and easy , convenience to install. It will stick to the  glass if installed carefully. According to the area, it may use 2 or 4 motors. It is widely used in huge building with glass roof. It is convenience to adjust  the light and keep the temperature. Providing a wonderful environment.