TM 9-2320-361-10 2-29. OPERATION OF TRACTOR AND FIFTH WHEEL (Contd) (5) Turn safety latch (16), left or right, to release locking plunger, and move operating handle (15) forward until it stays in forward position. Coupler jaws (9) are now unlocked. WARNING Do not back up vehicle without a ground guide, or injury or death to personnel may result. (6) Release parking brake lever (10), and slowly back tractor under trailer until fifth wheel coupling jaws (9) are securely locked around semitrailer kingpin (5). (7) Place transmission gearshift lever (11) in “N” (neutral) position and apply parking brake (10). (8) Make sure fifth wheel operating handle (15) is in rearward (locked) position, and safety latch (16) is in vertical position. CAUTION Be sure to couple emergency airbrake hose to trailer emergency coupling, and service airbrake hose to service coupling. Hoses not hooked up properly may cause failure in brake system. (9) Remove emergency airbrake hose coupling half (13) from hose support (12), and attach to trailer emergency coupling half (18). (10) Remove service airbrake hose coupling half (14) from hose support (12), and attach to trailer serviice coupling half (17). 2-137