90mm Storm Water Drain Outlet Flap Hinge

18 June -2017: Added 3 photos of an actual completed assembly, ready to be added to a drain pipe. The actual flap is just a piece of offcut acrylic I had lying around but it could be anything.

Where I live we have large pythons and, both to protect the snakes and to keep my pipes flowing, I have flaps on my stormwater drain pipe outlets to prevent snakes, rats and other small critters from entering the pipes. Using a grid on the end of the pipe does not work as grids catch leaves and gets blo