If you want to define the orientations of stacking a cargo, please use the direction enumeration. E.g. if you like to allow orientation #1 for stacking please give dir1 to the Orientation property of the cargo. Please see the following picture to understand the orientation 1,2,3,4,5,6. So giving dir1 + dir2 is the same meaning as the dirBasic . If you like to permit all orientations for stacking, please give the dirAll which is the same of dir1+dir2+dir3+dir4+dir5+dir6.