A kingpin is the metal pin on the bottom of the trailer that connects to the 5th wheel on the tractor or power unit. A king pin is actually a large steel plate about 5’ by 5’ feet that is welded to the bottom of the leading end of a trailer. Attached to the center of this plate is the kingpin. The kingpin is about 4” long and 2 ½” in diameter. The tractor’s 5th wheel is a 2’ diameter steel plate with a double set of jaws in the center which grab onto the kingpin. Although the connection is between the 5th wheel and the kingpin is incredibly strong, the 5th wheel is still able to pivot around the kingpin as the truck makes corners.  Arpin of RI uses Kentucky Trailers, the strongest, most durable moving trailers in the industry.