The answer to 'how does shut-off valve work' is that a shut-off valve is a valve used to control the flow of water or other fluids in a plumbing system. It is typically installed at the main water supply line or individual fixtures like sinks, toilets, and appliances to allow the water to be turned off for repairs or maintenance.
Shut-off valves work by using a handle or knob that can be turned to open or close the valve. When the valve is open, water can flow freely through the plumbing. When the valve is closed, it blocks the flow of water, allowing you to safely work on the plumbing without water spilling out.