A control device using a cylindrical- or conically- shaped plug with a hole through it that can be turned 90 degrees to the water or natural gas flow path to stop flow, or aligned with the flow path to allow the fluid to pass.
A valve with a revolving plug with an opening to permit passage of liquid when the opening is alined with the bore of the pipe.
Plug valves are valves with cylindrical or conically-tapered "plugs" which can be rotated inside the valve body to control flow through the valve.
Valve Cover, Pass Side
Those spark plug gaskets were a !@^% pain to get out. Thanks again, Audi.