A valve/plug assembly should be used to:

A valve/plug assembly is essential primarily to ensure that a system can be sealed and controlled properly, and this often includes the function of addressing missing components. In situations where a valve or plug is absent, the assembly can serve the specific purpose of replacing this missing element, thereby preventing leaks, ensuring safety, and allowing the system to function as intended.

The primary role of such an assembly is to control the flow of substances within pipes and other systems. While it can also be employed to check for leaks, regulate pressure, and ensure proper flow, these are secondary functions that come into play when the assembly is in place and operational. The core function revolves around ensuring that the connection is complete and sealed, addressing any failures that may arise from missing components.