From the development history of door studs, it can be seen that the initial function of door studs was only to strengthen the door core plate and threading, making it more sturdy and durable. However, in the feudal society, everything in architecture is not just for practical and beautiful purposes. In the process of development and use of some materials and components, due to the different class status of users, some building components have endowed people with consciousness and ideology, and inevitably gradually become the ritual symbol of the feudalism, as is the case with door pegs.
To be precise, nails are nails, and door nails are door nails. The specific surface meanings of the two are completely different. Nails are practical, their function is to connect and strengthen, they are just an iron nail; Once a nail transforms into a door nail, it is like a carp jumping over a dragon's gate, undergoing a qualitative leap and change. It possesses a special charm and meaning, balancing practicality with etiquette, symbolism, and appreciation, giving it life.
In the early stages of development, there were no strict usage regulations for door studs. In the early stages, the use of several routes and several door studs was not fixed and often varied with the assembly of the door. The number of routes and nails could be even or odd. As time passed, the demands of feudal etiquette permeated every corner of the building, and there was a mysterious sense of imperial power bestowed everywhere in the building. Door studs also began to have the symbolic significance of feudal etiquette demands. The trend of door studs is from scratch to existence, from few to many.
During the Northern Wei, Northern Qi, and Northern Zhou periods, archaeology and literature indicate that it was the earliest known time for the appearance of door studs. There is no fixed format for the number of paths and pieces of door studs.
In the Tang Dynasty, the form of the door was clearly depicted in Dunhuang murals, with a door anvil below, a threshold, a door forehead above, standing cheeks on both sides, a rooster perch on the forehead, and two door hairpins. The door panel was adorned with door studs and a headband. During the Northern Wei, Sui, and Tang dynasties, door studs were mostly used in the format of 5 routes and 5 pieces.
In the Song Dynasty, door nails were referred to as "floating hinges" or "floating rets". The Spring and Autumn Annals: "The Big Dipper has seven stars, and the Emperor has seven policies." In the Song Dynasty, door studs were already used in palaces and tombs, and most of the door studs on city gates and palace gates were in the format of seven routes and seven pieces.
The minority ethnic groups of Liao, Jin, and Yuan, as regional or national ruling regimes, mostly followed the architectural ideas and techniques of the Han people in the specifications and forms of palace architecture. However, the use of door studs was not limited to ancient systems. In the Liao Dynasty, the mountain gate of Dule Temple in Jixian County and the side hall of Wenshu Temple in Shanxi Wutai Foguang Temple in the Jin Dynasty, there were 6 door studs in each direction, and the door studs used the number of Yang, which showed a difference from the Yin Yang consciousness of the Han people.
The Ming Dynasty was a period in which China followed more ancient customs, and there were clear regulations on the use of door studs. The existing Beijing Forbidden City palace complex shows us that the royal palace used door studs in a format of 9 per door, 9 per road, a total of 81 (multiples of 9). 9. In ancient Chinese numerals, it is considered the largest yang number. "Nine five, flying dragons are in the sky, making it easy to see adults." This is the etiquette of the emperor. Therefore, royal architecture often uses the nine five system to represent imperial power. The doornail uses the positive number of 9 to represent the maximum imperial power, which is perfect and beautiful.
In addition to the royal palace, the Ming Dynasty also stipulated that door studs could be used for the main entrance of the Prince's Mansion. According to the "Da Ming Hui Dian", the system of the royal palace is as follows: "According to the ancestral teachings, all royal palaces should be built according to the established format, and no division is allowed. In the fourth year of the Hongwu reign, the system of the imperial palace was established, with... four gates, and... the main gate was painted with red paint, gold, and copper nails." According to regulations, the royal family royal palace can use door nails, without violating the system. The Duke and Marquis's Mansion stipulated that the doors should be decorated with gold paint and animal faced tin rings, the first and second grade official doors should be decorated with green oil animal faced tin rings, the third to fifth grade official doors should be decorated with black oil tin rings, and the sixth to ninth grade official doors should only use black door iron rings. Duke and even the ninth grade officials were not allowed to use door nails, indicating the etiquette system of using door nails in Ming Dynasty architecture.
However, there is no literature on how to use door nails and distinguish ritual sequences between the royal and royal families in the Ming Dynasty. The imperial architecture has been certified for the construction of the Forbidden City Palace, while it is unclear how many rows and several door studs were used at the gates of the Ming Dynasty palace. According to the latest report from the China Cultural Relics Daily, the tombs of the Ming Dynasty King of Shu and his consorts have been excavated in Panjiagou Village, Jinjiang, Chengdu, Sichuan. Tomb No. 1 is divided into three chambers, namely the front, middle, and back, and a coffin chamber, each separated by a stone gate. There are 81 stone breast nails chiseled on the stone door of the front chamber, in 9 rows and 9 rows, all coated with gold and now partially detached. The excavation of the tomb of the Ming Dynasty King of Shu provides us with a basis for the actual use of door studs in the Ming Dynasty royal palace.
In the Qing Dynasty, there were detailed and strict regulations on the use of door nails. The royal architecture inherited the regulations of the Ming Dynasty, while the regulations of the royal mansion were different from those of the Ming Dynasty. In the ninth year of the Shunzhi reign of the Qing Dynasty, the system of the royal mansion was established, with three out of sixty gold nails for each door, meaning that each door had nine routes and seven nails for each route, totaling 63 nails per door. Under the system of the Crown Prince's Mansion, the gold nails on the main gate were reduced by two-thirds to the Prince, with each door having 9 routes and 5 routes, totaling 45 door nails per door. The system of the Prefectural Prince's Mansion, Baile's Mansion, Beizi's Mansion, Zhenguo's Mansion, and Fuguo's Mansion is the same as that of the Imperial Prince's Mansion, which means that each door has 9 routes and 5 routes, with a total of 45 door nails per door.
The "Engineering Practice of the Ministry of Works" issued by the Yongzheng Dynasty of the Qing Dynasty also had strict regulations on the installation of door nails: "For door nails, the width of each nail from the inside to the outside of the door leaf should be determined by its circular diameter. The height and diameter of the door nails should be the same. If nine nails are used, there should be a number of diameters for each nail, and the gap should be taken as one blank for each nail diameter. If seven nails are used, there should be a number of diameters for each nail, and the gap should be taken as two blank for each nail diameter. If five nails are used, there should be a number of diameters for each nail, and the gap should be taken as two blank for each nail diameter.
In a feudal society with strict hierarchy, there are strict regulations on the use of door studs for building doors, such as the number of door studs used, the size of the circular diameter of the door studs, and the distance between them. Door studs are divided into nine, seven, and five ways according to the user level. The Royal Palace uses nine routes, with the highest level. The Book of Han states: "From top to bottom, descending to kill with two, ritual also", which means using numbers such as 9, 7, and 5 with a tolerance of "2" to express the level of ritual system. The clear regulations on the use of door studs in the Qing Dynasty were based on the traditional Chinese etiquette system, which endowed the use of door studs with a sense of etiquette and became an information carrier for feudal hierarchical symbols.