(1) A fifth wheel coupling, the mating parts of a coupling, a kingpin or towbar must not be used in a light combination for a load more than the manufacturer's load rating.(2) A kingpin in a light combination must be used only with a fifth wheel coupling that has a corresponding jaw size.
Example:
An adaptor must not be used to fit a kingpin to a fifth wheel coupling
(3) The mating parts of a coupling used to connect a light semi-trailer to a towing vehicle must not allow the semi-trailer to roll to an extent that makes the towing vehicle unstable.