semi truck bobtail backing up to couple the fifth wheel with the trailer - King pin - part of the trailer that engages with the truck bed or fifth wheel

semi truck bobtai backing up fifth wheel king pin trailer truck coupling transport tractor connection lorry chassis fifth service hook hitch rear dirty traction coupling device semi tires industrial hooking up grease kingpin maintenance towing hook trailer coupling underside vehicle cargo carriages logistic freight equipment 5th warehouse distribution centers logistics freight industry copy space reefers dryvan dry vans flatbed connestoga american truckers cdl holders