a plurality of collapsible arms each interconnecting and extending between said base and said curtain-supporting frame and being movable between a collapsed position in which said curtain-supporting frame is disposed generally adjacent said base and an extended self-supporting position in which said curtain-supporting frame is disposed in an operative position elevated above said base, each of said arms comprising a plurality of links pivotally interconnected together, means at each interconnection adapted to releasably retain said links in said extended self supporting position of each of said arms and said means permitting collapse of said links into a stacked relation with one another between said frame and said base in said collapsed position of said arms upon the application of pressure to said frame in a direction normal to and towards said base