Yingzao Fashi
The construction of wutomen was standardized in the "Yingzao Fashi" of the mid Song dynasty. It consisted of two posts and a horizontal beam forming a frame and two doors. By the Ming and Qing dynasties, it was called a "pailou" or "paifang", and evolved into a more elaborate structure with more posts and gates, with a superstructural gable on top; the highest rank was a five gate-six post-eleven gable pailou.