It used to be common in rural areas in the south of the Yangtze River and Hangzhou. There are usually two small doors outside the gate, half of which are installed on the threshold. What are their names? According to the information provided, this kind of small door is called waist door, also called low door or security door. It often appears in rural areas in the south of the Yangtze River and Hangzhou, and often appears in front of houses and buildings. The waist gate is about half the height of the gate, just to the waist of adults, hence the name. Its main function is to illuminate and prevent animals from entering the home.