When coupling a converter dolly to the rear trailer, what safety device must be connected in addition to the pintle hook?

SAFETY CHAINS ON THE CONVERTER DOLLY: When connecting the dolly's drawbar/tow bar eye to the pintle hook of the trailer ahead, SAFETY CHAINS must also be connected. PURPOSE: They serve as a backup — if the pintle hook connection fails or comes loose, the safety chains help keep the dolly and rear trailer attached, preventing complete separation; a trailer that fully separates at speed is catastrophic; PROPER CONNECTION: Chains crossed and secured per the equipment design, with enough slack to allow turning but not so much that they drag; PINTLE HOOK: The pintle hook (on the rear of the first trailer) and the lunette eye (on the dolly tow bar) form the primary connection; it must be fully latched and locked; INSPECTION: Verify the pintle hook is closed and locked, safety chains are connected and secured, the connection is tight, and the dolly is properly coupled at both ends (pintle hook to front trailer AND fifth wheel to rear trailer); the additional coupling points in doubles/triples mean more connections to secure and inspect; safety chains are a critical backup, and their connection is verified during coupling and inspection.