Centering door introduction: On Banner Street, whether it has four doors or six doors, the middle door is uniformly covered with a low wooden door 4.7 feet high and 3.6 feet wide, with a hollow at the top. Small window, this kind of door is called "centering door", also known as "liuli door". The "Liu Li Gate" is only opened during weddings and funerals, and is usually kept closed. The small hollow window on the center door is a small window for the female family members of the bannermen who cannot be seen in public to watch the street scene and provide ventilation.