Those who visit the Palace Museum are impressed by the grandeur of the imperial architectural complex. However, they seldom notice the detail of the bracket sets (dou gong) placed under the roofs, a complicated system tenoned by timber components. Bracketing system in buildings in the Palace Museum is similar to but much smaller in scale than those on the buildings dating to the Tang and Song dynasties (seventh to thirteenth centuries). The reduction in size in timber structures suggests that they no longer played such an important role in the column roof relationship. Although bracketing systems appeared in various forms, in most cases they were for decoration rather than for structural support.
  In the Forbidden City, which was the imperial palace for twenty four emperors of the Ming and the Qing dynasties (from 1420 to 1911), the bracket sets that you see are characterized by many variations and sophisticated systems. Generally speaking, there are exterior and interior bracket sets. The cluster that rests immediately on the top of a column is called "capital bracket" (zhutouke dougong). Those in between them are "intercolumnar brackets" or "span brackets" (pingshenke dougong), and if the back sticks upward it is called "gilded bracket sets" (liujin dougong). Brackets sets placed at the corners of a building are "corner bracket sets" (zhuanjiaoke dougong). Inside a building, you will also find bracket sets lodged between beams and purlins.
These are only sweeping generalizations. Given the status of the building, each variation of bracket sets can be classified according to the tiers or "steps" (cai) that make up a bracket set cluster. They can be of three, five, and even eleven steps. The more steps the bigger a cluster.
  Other than a whole piece, a bracket set is made up of a block (dou) and arms (gong) that are joined together by mortise and tenon. Sizes of blocks and arms were made in proportion to the measurement of the mortise on the cap block. Therefore, clusters of bracket sets, even though of the same tier, might be of different sizes. In an encircled courtyard, buildings with different types of bracket systems appear higher and lower, creating a rich space with a toothed skyline.
  The bracket sets mentioned above were named in the Ming and Qing dynasties, which were considerably different from the terms of the Tang and Song dynasties. The history of bracket set changes equates with the historical development of Chinese architecture. Millions of various bracket sets establish the splendor of traditional Chinese architectural culture.

  The Forbidden City is a world populated by dragons. Whether looking above or below, near or far, you will find dragon designs glimmering.
  As the abode of the emperor, the Forbidden City was overwhelmingly embellished with various patterns of dragons. In ancient China the dragon was considered the most powerful of all creatures. In the third century of the Common Era, after the Han dynasty (206 BCE 220 CE), the dragon was increasingly identified with enlightened and virtuous emperors. Every potentate styled himself a "reincarnated dragon and the son of heaven", proclaiming that he was the most significant person under heaven. Using comparisons to dragons, emperors deified themselves. The five clawed golden dragon   the highest reification of the symbol  became the major decorative design in the Forbidden City. (Sumptuary laws were enacted to restrict its use to the imperial family.)
  In the Chinese philosophy classic The Book of Changes (Yi jing), the first divination trigram is qian. It represents "heaven", the strongest hexagram the fifth NINE blematic of a flying dragon in the sky. Accordingly, the emperor was referred to as the "Venerated Nine five", and everything about him was associated with the numbers "five" and "nine". In the Hall of Supreme Harmony (Taihe dian), for example, the back of the throne is decorated with nine entwined golden dragons. Another example is the sign board bearing the inscription "Upright and Clearly Illuminated" (Zhengda guangming) that hangs in the Palace of Heavenly Purity (Qianqing gong); its lower edge is painted with five golden dragons. On the magnificent glazed tile screen outside the Gate of Tranquil Longevity (Ningshou men), nine flying dragons are carved in five groups.
  In the Forbidden City, dragons not only soared up the imposing buildings, but also permeated the atmosphere around the emperor, from robes, furniture, clocks, implements on writing tables, and eating utensils, to weapons, ceremonial armor, and many other objects relating to imperial life.
  In ancient Chinese folklore, the dragon has nine sons, each with a different temperament and distinctive predilections. Luckily we are able to find them on the gates, roof ridges, incense burners, and musical instruments in the Forbidden City.
  In addition, the large imperial art collections included objects of great antiquity that are decorated with dragons. Delighting viewers with unusual designs and vibrant manifestations, the dragons are emerging from mist or writhing in the vast sea; some are powerful, some are vigilant, some are agile and clever, others are dignified and stately. All kinds of divine dragons assemble in the Forbidden City.