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，且压力大于盖土网 防寒布 麻绳 油麻绳 麻刀 沥青麻绳 静压造型线 自动浇注机 铸铁拍门 钢制拍门 玻璃钢拍门管内压力时，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