This invention relates generally to a conveyor assembly for separating and aligning parcels, packages, bags and other articles prior to processing with a singulator. The stepped wall assembly includesa low friction conveying surface having both forward and lateral conveying forces for moving articles toward a lateral sidewall and a downstream conveyor. A series of offsets disposed between straight and diverging sidewalls force parcels toward the center of the conveyor against the lateral forces of the low friction conveying surface gradually separating and converging the parcels toward a selected sidewall of the conveyor and in line with a singulator apparatus.