PurposeUSED TO CHECK THE ACTUATING PRESSURE OF HORIZONTAL STABILIZER FUEL TANK PRESSURE RELIEF VALVES AND WING SURGE TANK PRESSURE RELIEF VALVESAirplane737, 747, 757, 767, 777-200, 777-200ER, 777-200LR, 777-300, 777-300ER, 777-8, 777-9, 777FUsage CodeMAINTENANCE 