Why did the ancients set a threshold at the door? What is the function of the threshold?

1, the ancients put the threshold at the door, originally designed to improve air tightness and reduce air circulation. The ancient threshold is a symbol of power and status. The higher the threshold, the more distinguished the host.

The threshold originally refers to the crossbar under the door. There must be a threshold in front of a traditional house in China. People have to cross the threshold when entering or leaving the gate, which plays a role in buffering the pace and blocking external forces.