In the past, houses were mostly built in the form of "quadrangles". The main room is the main hall, the rooms on both sides are the main room, the main room on the left and the secondary room on the right. The house in front of the main room and the secondary room is a wing, also called the south wing and the north wing or the east wing and the west wing. The south house cannot be higher than the main house, that is to say, the roof of the north and south house cannot be higher than the roof of the main house.