Stopcock

The only consistent attribute is that the valve is designed to completely stop the flow when closed fully.

Stopcocks are used to grossly regulate the flow of tap water in residential and commercial services.

One is found at the junction of a water main and the branch leading to an individual service (allowing the service to be isolated from the main trunk), and a second inside the structure (allowing its plumbing to be isolated from the branch line leading into it).

The stopcock is a smooth tampered plug or rotor with a handle, which fits into a corresponding ground glass female joint.

The stopcock is held together with the female joint with a metal spring, plastic plug retainer, a washer and nut system, or in some cases vacuum.

Example of symbol for a stop valve.
A single hole hollow glass stopcock held in place by vacuum