Casement windows are divided into sliding type and top-hung type. Its advantages are large opening area, good ventilation, good sealing, excellent sound insulation, heat preservation and seepage resistance. The inner opening type is convenient to wipe the window; the outer opening type does not take up space when opening. The disadvantage is that the window width is small and the view is not open. Outward-opening windows open to take up a piece of space outside the wall, easy to damage when scraping high winds; and inward-opening windows are to take up part of the indoor space, the use of screens is not convenient, the use of screens, curtains and other inconvenient when opening windows, such as quality is not good, but also may seep rain. Advantages are simple, beautiful, large window width, large glass block, open view, high light rate, easy to wipe the glass, flexible, safe and reliable, long service life, open in a plane, occupy less space, easy to install screens, etc.