Volvo VNL 780 Operator's Manual page 370

360 OPERATION
Make sure the trailer kingpin is in the jaw slot and that the jaw is closed behind the pin. The
kingpin should not overhang the fifth wheel or be caught in the grease groove.
To verify that the kingpin is actually in the fifth wheel slot and the jaw is closed, the pin
must be visually inspected from the rear. Use a flashlight if necessary.
W9000181
Make sure the trailer bed is resting on the top surface of the fifth wheel plate, and that there
is no visible gap between the fifth wheel and the trailer bed plate.