The function of the threshold is to separate the inside and outside. At the same time, it can protect the bottom of the door and block the wind blowing in from under the door. But more importantly, the threshold also reflects the dignity and identity of the owner; among the people, the threshold is the owner's neck or back, and it is taboo to step on it with your feet.
The "Book of Rites" says: "When officials enter and leave the monarch's door, they do not violate the threshold." This means that when a minister enters the monarch's door, he should turn sideways from a short log erected in the center of the door. But don't step on the threshold (threshold) with your feet. In the Han and Jin Dynasties, the worship of door gods became popular, and the act of sacrificing doors evolved from temple rituals to social customs. "It is now a custom in the state to worship the door while looking at the sun." ("Jingchu Years' Notes" by Liang Zongping of the Southern Dynasties). The production of thresholds is also very particular, with high height from the ground and beautiful packaging being the most important. Especially for those wealthy houses, they compare with each other and do not want to be inferior to others. In common sayings that have been passed down to this day, it is often said that a certain family has high standards, which means that the family has good conditions and respectability in all aspects.
In the old days, all doors were made of wood, and the ground was mostly uneven, so the bottom of the door and the ground could not be completely sealed. As time went by, the wooden doors gradually decayed, the ground became pitted, and the door gaps became wider. Come bigger.
Building a threshold, on the one hand, has a structure like the upper and lower rows of teeth, which can better achieve close contact. Secondly, in Feng Shui, the threshold means blocking external adverse factors from entering the home, and also prevents Family wealth is exposed.
From Zhihu, for reference only