A packaging container/case is formed of two cooperating cartons, the cartons formed of similar or identical blanks. Each carton includes a first major panel and an opposite second major panel, with a first major panel extension extending from the first major panel. The two cartons are joined by securing each first major panel extension to the second major panel of the other carton, providing unbroken major panels for the assembled case. The minor panels/ends are also unbroken. Each extended first major panel and extension includes an unbroken upper closure flap extending the length of the panel and extension, which with the minor panel closure flaps extending from the top of the opposed ends of each carton, provides conventional upper closure for the assembled case which can be sealed using standard packaging machinery. The bottom closure flaps are conventional each carton of the case, although the upper closure may be applied to the lower closure flaps if so desired. The resulting coplanar flap surfaces, with the unbroken sides of the assembled case, provide stacking and compact storage of such cases as required. Tear strips and/or score lines may be formed vertically down the center of the extended major panels and panel extensions, to provide for separation of the two cartons forming the case without need for tools. Preferably, the two cartons are equal in size and rectangular. However, the present construction may also be applied to two mating cartons of unequal size and/or congruent trapezoidal shape.