the.com/valves
Doors for fluids that only know how to swing one way.
means Devices that control flow direction or pressure in pipes, engines, hearts, and other plumbing both mechanical and biological.
from From Latin valva, a leaf of a folding door — the same hinged swing your aorta performs about 100,000 times a day.
Heart countFour valves keep your blood from backsliding.
Old radiosVacuum tubes were called valves for steering electrons.
Brass instrumentsTrumpet valves reroute air to change pitch.