A dictionary isn't much help for me in this case as I don't even know if there is an equivalent in my native tongue, so I don't know what to look for.
I have to describe what I mean:
Consider a truck pulling a trailer that only has an axle (or axles) at the back of the trailer. The front of such a trailer rests on a horizontal mount-plate located above the back-axle(s) of the truck.
This arrangement is also sometimes found on bigger model pickup-trucks to enable them to pull such trailers.
I don't mean the hook found at the back off a regular car to which you can hitch a trailer or caravan.
Or the heavy duty hitch arrangement to put a trailer (with axles front and back) after another trailer. (Also found sometimes at the back of lorries, tractors and some trucks.)
Is there a proper word (or phrase) for this mount-plate in English?