In what context is a 'gate valve' most commonly used?

A gate valve is primarily designed for shutting off the flow of liquids and gases in a pipeline. When the valve is fully open, it allows for a straight-line flow with minimal restriction, which is why it is not typically used for flow regulation or pressure reduction. The primary function of a gate valve is to start and stop the flow of fluid; it is not effective for throttling or controlling flow rates due to the design of its closure mechanism.

In applications where isolating a section of the pipeline is necessary, such as maintenance or emergency situations, the gate valve serves effectively to provide a tight seal when closed. While it can prevent backflow to some extent when closed, that is not its primary design goal. Thus, its most common use is indeed for shutting off the flow.