What is the primary use of a piercing nozzle?

The primary use of a piercing nozzle is indeed to penetrate metal surfaces. This specialized nozzle is designed to create an opening in materials that are otherwise difficult to breach, such as metal roofs or walls, thereby allowing water to be effectively applied inside a fire location. By delivering water directly into a compartment that is inaccessible through traditional firefighting methods, the piercing nozzle can help control or extinguish fires more efficiently, particularly in situations where access is limited.

While other options may seem relevant in a broader context of firefighting, they do not capture the specific functionality of a piercing nozzle. It is not intended for the connection of hoses to hydrants, the regulation of water flow, or specifically targeted at extinguishing fires in high-rise buildings. Such nozzles have a unique operational role that distinguishes them from other tools and equipment used in firefighting scenarios.