18 is determined by three pins actually the machine is provided with six pins with half of them being visible in the figures truck bed 16 includes an upright member 104 terminating in three holes 106 108 and 110 disposed along a substantially horizontal plane a pin 112 disposed in hole 108 in the figures secures the frame 18 to upright 104 through a corresponding hole not shown in the frame 18 truck 16 further includes a horizontal extension 114 with a plurality of holes 116a i frame 16 also has a corresponding lip 118 with a hole not shown and a pin 120 is passing through lip 118 to secure it to extension 114 via one of the holes 116 more particularly hole 116g as shown in fig1 finally above upright 104 frame 18 has another hole for engaging through a pin 122 the arm 124 of a hydraulic cylinder 126 the end opposite arm 124 cylinder 126 has a pin 128 disposed in a diagonal slot 130 of a vertical wall 132 vertical wall 132 is secured to truck 16 the arrangement in fig9 12 is used to position the frame 18 vertically initially as previously mentioned the frame extends vertically along the truck 16 in this position arm 124 is disposed substantially within cylinder 126 and pin 120 is not installed after the truck is positioned at the desired location cylinder 126 is activated forcing arm 124 to extend thereby rotating frame 9 clockwise around pin 112 until it reaches a substantially vertical position once the frame is vertical pin 120 is installed to maintain the frame in its position because of the large number of holes 116 provided the frame may be fixed in a wide range of positions defined by angle o in.