They're talking R.v./mobile home dealer. Also, you may wish to try the type of dealer where smaller utility trailers are built or sold-you know, like small car-towing trailers, box or utility trailers that you would pull with your car or light-duty truck.
A "take-off" wheel is one removed from a new (or almost new) vehicle in order to be replaced with an upgraded wheel and tire package.
Hope this helps clear up your questions.
Regards,
Wannabe
