Abstract: An elongated horizontal base member is provided for mounting in transverse position on one end of a towing vehicle. A pair of horizontal support arms have a first pair of corresponding ends thereof mounted on the base member, at points spaced therealong, for shifting along the base member and swinging relative to the base member about upstanding axes shiftable along the base member with the first pair of arm ends between first outwardly convergent positions and second substantially aligned positions generally paralleling the base member with the first pair of arm ends disposed remote from each other and the second other pair of arm ends disposed adjacent each other.