containers of the wraparound and tray style are provided , having enhanced stacking strength and general robustness , through the provision of internal and external reinforcing panels and flanges . variations of the basic invention are provided with closure flaps of varying configuration and placement ; end walls and minor flaps with angled side edges to provide for containers having inclined sides ; regions of weakness , removable portions of panels and / or preformed apertures to permit conversion of the containers to display / merchandising modes ; gusseted corner structures to provide for containment of fluent materials ; and enhanced transverse support structures .