拍门是安装在江河边排水管出口的一种单向阀，当江河潮位高于 出水管口，且压力大于管内压力时，拍门面板自动关闭，以防江河潮水倒灌进排水管道内。主要安装在排水管道的尾端，用于防止外水倒灌。适用于水利系统、市政 污水、城市防洪排涝、污水处理厂、自来水厂等。
Clapper gate is a one-way valve installed at the outlet of the drainage pipe by the river. When the river tide level is higher than the outlet pipe and the pressure is higher than the pressure in the pipe, the clapper gate panel will automatically close to prevent the river tide from pouring back into the drainage pipe. It is mainly installed at the end of the drainage pipe to prevent backflow of external water. It is applicable to water conservancy system, municipal sewage, urban flood control and drainage, sewage treatment plant, waterworks, etc.