Motor vehicle trailer with counterbalancing weights

A trailer with front and rear ends and lateral sides comprising at least two vertical walls, a floor and a top thereof which together define an interior space, wherein said floor of said trailer is provided with a plurality of recesses sunken below a level of the floor, said recesses each having a horizontal perimeter, said perimeter closely engaging an exterior surface of a horizontal cross-section of one of a plurality of rigid counterbalancing weight means for counterbalancing the contents of said interior space of said trailer so as to provide stability in use wherein said plurality of recesses are disposed adjacent said front and rear ends, and adjacent lateral portions of said floor of said trailer, and wherein said counterbalancing weight means are shaped so as to be interchangeable between said recesses so as to provide proper weight balance for said trailer depending on the position of the contents of the trailer.