拍门--主要安装在排水管道的尾端，用于防止外水倒灌。材质分为不锈钢、铸铁、型钢、复合材料(玻璃钢)等多种材料。
Flap door - mainly installed at the end of drainage pipe, used to prevent external water from flowing back. Materials are divided into stainless steel, cast iron, steel, composite materials (glass fiber reinforced plastic) and other materials.
而拍门又分为很多种，比如，浮箱式拍门，平板式拍门，套筒式拍门等等。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。
There are many kinds of flap doors, such as floating box type, flat plate type, sleeve type and so on. It is a kind of one-way valve installed at the outlet of the river drainage pipe. When the tide level of the river is higher than the outlet pipe mouth and the pressure is greater than the pressure in the pipe, the flap door panel will automatically close to prevent the river tide from flowing back into the drainage pipe