The advantages are simple and beautiful, large window width, large glass block, wide field of vision, high lighting efficiency, convenient glass cleaning, flexible use, safe and reliable, long service life, opening in one plane, less space occupation, convenient screen installation, etc. At present, sliding windows are the most widely used. The disadvantage is that the two windows cannot be opened at the same time, and can only be opened half at most, so the ventilation is relatively poor; Sometimes the sealing performance is also slightly poor. Sliding window: it can be divided into left and right, up and down sliding windows. Sliding windows have the advantages of not occupying indoor space, beautiful appearance, economical price and good sealing. High grade slide rails are used, which can be opened flexibly with a slight push. With large pieces of glass, it not only increases the indoor lighting, but also improves the overall appearance of the building. The stress state of the window sash is good and not easy to be damaged, but the ventilation area is limited.