The glass of casement window is mounted on the window sash, which is connected to the window frame by hinges , with internal and external openings. It is simple in structure, convenient in production, installation, maintenance and opening, and is the most widely used in general buildings. The advantage of casement window is that it has a large opening area, good ventilation, good sealing, sound insulation, heat preservation and excellent impermeability. The inner opening window is equivalent to the outer opening window, which has high safety and convenient cleaning. The disadvantage of the inner window is that the inner window will occupy the indoor space, easy to bump, and the use of curtains is not convenient;