Question A shut-off valve is: Answers A device that prevents air from escaping an air brake system. A substitute for a pintle hook. Another name for a glad hand. Explanation Shut-off valves are used in air supply lines to control the passage of air from one trailer to another. The rear shut-off valve should always be closed to prevent air from leaving the braking system. Take a FREE Practice Test Now This questions appears in the following tests: California Double ,