Where are shut-off valves?
Answer: Service and supply air lines at the back of trailers. Shut-off valves (also called cut-out cocks) are used in the service and supply air-lines at the back of trailers used to tow other trailers. These valves permit closing the air-lines off when another trailer is not being towed. You must check that all shut-off valves are in the open position except the ones at the back of the last trailer, which must be closed.
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