on the roadway in a normal manner while using the conveyor 94 in operations requiring the discharge to the right side of the truck i e the side opposite discharge opening 96 in addition discharge opening 96 can also be used for some other operations while the spreader box 12 is in the position shown in fig6 also it is most convenient to have the spreader box 12 in the position shown in fig6 when adjusting the position of the bar 112 and road wheel 104 as described above to change the elevation of the top surface of the material the shoulder of a road often is sloped away from the main surface of the road in order to facilitate drainage the embodiment of my invention shown in fig7 and fig8 is particularly well suited to the resurfacing of such shoulders in this embodiment the back wall 18 is comprised of a short section 142 rigidly attached to first side wall 14 and a long section 144 back wall sections 142 and 144 are rotatably connected near the bottom by a hinge 146 comprised of a pin 147 through corresponding holes in the two back wall sections a slot 148 comprising part of the diameter of a circle about hinge 146 is cut in back wall section 144 near the top thereof a pin 150 is rigidly attached to back wall section 142 and projects through slot 148 to provide support for back wall section 144 a short bar section 152 having a transverse threaded hole 154 therethrough is rotatably attached to the outside of back wall section 144 by means of bracket 155 bar 152 is located on the.