The HCW tidal flap with incorporated fish friendly flap(s). They slowly closes as the tide rises and pulls the flap shut using the float. This ensures a greater period of time where the flap is open and submerged giving fish and eels more time to pass through. HCW Larinier fish Passes made from HDPE are for improving fish migration suited for mounting on to fixed structures.Do you want to know more or do you have any questions please do not hesitate contact us. We are happy to assist you.