Abstract: A container bag (10) having a base (14), side walls (12) and lifting loops (16) is characterized in that the central portions (15) of the side walls of the bag or of a liner within the bag are stiffened relative to the corner portions whereby to effect a squarer shape to the bag. The stiffening may be achieved by fabric from which the bag (or liner) is to be made being selectively stiffened in those areas destined to form the central wall portions by using different weave densities, more or additional threads of either the same or a different kind, additional layers of material being attached e.g., by adhesion in the relevant areas, or a stiffening coating composition e.g., of a polymer applied.