Plastic Flap Valves

plastic
A synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon, etc., that can be molded into shape while soft and then set into a rigid or slightly elastic form
fictile: capable of being molded or modeled (especially of earth or clay or other soft material); "plastic substances such as wax or clay"
generic name for certain synthetic or semisynthetic materials that can be molded or extruded into objects or films or filaments or used for making e.g. coatings and adhesives
capable of being influenced or formed; "the plastic minds of children"; "a pliant nature"
Credit cards or other types of plastic card that can be used as money

valves
A cylindrical mechanism in a brass instrument that, when depressed or turned, admits air into different sections of tubing and so extends the range of available notes
(valve) device in a brass wind instrument for varying the length of the air column to alter the pitch of a tone
(valve) control consisting of a mechanical device for controlling the flow of a fluid
A device for controlling the passage of fluid through a pipe or duct, esp. an automatic device allowing movement in one direction only
A membranous fold in a hollow organ or tubular structure, such as a blood vessel or the digestive tract, that maintains the flow of the contents in one direction by closing in response to any pressure from reverse flow
(valve) a structure in a hollow organ (like the heart) with a flap to insure one-way flow of fluid through it

flap
(of a bird) Move (its wings) up and down when flying or preparing to fly
(of something attached at one point or loosely fastened) Flutter or wave around
any broad thin and limber covering attached at one edge; hangs loose or projects freely; "he wrote on the flap of the envelope"
roll: move in a wavy pattern or with a rising and falling motion; "The curtains undulated"; "the waves rolled towards the beach"
dither: an excited state of agitation; "he was in a dither"; "there was a terrible flap about the theft"
Move (one's arms or hands) up and down or back and forth