Fifth Wheels 1 2 2 1 3 3 4 4 A B f310532 07/26/96 A. Closed Position, Locked B. Open Position, Unlocked 1. Release Arm 2. Release Handle 3. Lock Pin 4. Hinged Lock Fig. 11.4, Type "A" Kingpin Lock Mechanism WARNING and loss of vehicle control, possibly resulting in serious personal injury or death. Do not overload any tractor axle by improperly loading the trailer. This could cause erratic steering Unlocking the Fifth Wheel Lock Mechanism 1. Apply the tractor parking brakes. 11.5