But that's like buying an automobile with the gas-line valve shut as the default configuration.

Scallops have simple eyes around the margin of the mantle and can clap their valves shut to move sharply, hinge first, to escape from danger.

As the camshaft lobe enters the lift phase of its travel, it compresses the lifter piston, and a valve shuts the oil inlet.

A production retainer valve shuts in the riser and the annulus master valve shuts in the riser.

These are used in cases where accidentally shutting the valve would have severe consequences, or any application where the end user prefers a mechanical device.