A brass concealed stop cock is a type of plumbing valve that is hidden from view behind a wall or other structure. It is used to shut off the flow of water from a water supply line, often in an emergency situation. The stop cock is typically located in a utility room, basement, or other area away from the main living space. It is often the only way to shut off the water supply to an entire house or building. The brass material makes the stop cock highly resistant to corrosion, ensuring it will last for years.