Valves

Gate valves are the most used valves.
Ball valves use a metal ball with a hole bored through the center to control flow.
A Butterfly valve is used for flow regulation in large pipe diameters.
A Needle valve can be used to regulate flow of a substance, usually either gas or water, through an appliance or system.
Check valves are used in a wide variety of applications including line isolation, priming pumps, media injection, maintaining head pressure, and many other uses.