Pay attention to the doornail:
Door nails were also called "floating nails" in ancient times. "Floating nails" are bubbles on the water, which are the unique decoration of the gates of traditional buildings in China. They are usually found at the palace gates, yamen gates and temple gates. The rows of huge golden doornails on the solid flat door not only make the locked door look solid and dignified, but also present a magnificent atmosphere, which multiplies the magnificent beauty of the building.
The doornail evolved from functional parts in history, and its original design was particularly practical. It originated from one of the measures of fire attack on the door leaves of ancient city gates, and was used to fix and smear the soil on the door leaves. The use of doornails on city gates first appeared in Sui and Tang Dynasties. At the beginning, for structural needs, nails were nailed on the boards and belts to prevent the door panels from loosening. However, because the nail cap exposed on the surface of the door is unsightly, for the sake of beauty, people make the nail cap into the shape of a bubble head, so it has a decorative effect. The doornail is very long in both vertical and horizontal directions, and the projection of circular volume is proportional to the heavy door leaf, which is spectacular enough.
The Forbidden City used to be called the Forbidden City. South (Wumen), North (Shenwumen), West (Xihuamen) and East (Donghuamen) all have golden gate nails. The number of doornails was not specified before the Ming Dynasty. In the Qing dynasty, there was a hierarchy. Only the palace gate can be used the most "nine rows and nine columns", and the nine-way doornail embodies the highest level of doornail arrangement. With the different status and rank, the number and arrangement of doornails are different in Wang Mi, Wang Fu County and temples. Generally, the residence of the prince is vertical and vertical; The Prince's Mansion is vertical seven and horizontal five; The doors of the Duke's Mansion are seven in vertical and horizontal directions, and five in vertical and horizontal directions from Marquis to Baron. In addition to the palace gate, other doors can only be nailed with iron gates, not copper; Civilians can't use doornails at all.
There is still a mystery about the doornail of the Forbidden City. There are nine doornails in the south, north and west gates, and eight rows and nine columns in the east gate. Why use even numbers instead of odd numbers here? It is said that the Lord of Donghuamen is in mourning, so the number of doornails is counted by Yin. The reason is that when the first emperor's burial palace stopped at Jingshan Shouhuang Hall, it was from Donghuamen. However, some people have verified that the coffin was carried in Xihuamen, and it is said that the emperor also visited Donghuamen. Maybe it will take time to solve this mystery.