According to the historical records, bamboo cages are also called "Macha"or "Zhuluo" which are made of local Ci Bamboo or Baijia Bamboo. Filled with pebbles, they are used to protect the banks. Li Bing adopted this method in the Dujiangyan Project which cost little but functioned much. This technology is used till today. Bamboo cages can be made easily and used conveniently which are one of the most important tools in the project.