a supporting frame having first and second substantially parallel right angle plates; and

a first pair of levers hinged both to the first right-angle plate and to a first lock member and a second pair of levers hinged both to the second right-angle plate and a second lock member, wherein the lock members and pairs of levers are movable between first positions to second positions where the lateral distance between the lock members in the second position is greater than at the first position and wherein in the second position the lock members are in contact with respective lower arms of the three-point hitch.