A display case for a replacement window, comprising a case assembly and frame member. The case assembly has a front panel and a rear panel hingedly connected to each other near their top edges, and having an inwardly directed flange connected to their side edges. The frame member secures a replacement window therein and is slidably inserted within the case assembly. The frame member comprises two side sections, a top section and a bottom section. Each side section has at least one longitudinally-extending channel on its external surface for sliding engagement with a flange on the case assembly. The case assembly has means for preventing opening of the hinged connection beyond a predetermined maximum point. There is a plank attached to said bottom section of the frame and extending along its length. The plank has outwardly beveled longitudinal edges so as to create a groove between the bottom section of the frame and the bottom of each beveled edge. Sliding the frame out of the case assembly and opening the hinged connections to their maximum point causes the top edges of the panels to engage the grooves and lock the frame in an extended position. Closing the panels releases the grooves and allows the frame to slide within the case assembly for transportation and storage.