Introduction to the Dujiangyan Horizontal Rail: The Horizontal Rail is the standard for beach washing buried in the "Fengqiwo" of the Neijiang River. It is also a symbol of the depth of the river bed that is cleaned up every year in the Neijiang River. According to legend, when Li Bing built the weir, he buried a stone horse under the riverbed of the Neijiang River, which served as the standard for the depth of the beach every year. It later evolved into a lying iron.