Abstract: A collapsible panel structure consisting of at least one rod member, restraint elements secured to the rod member and a removable stress device acting to exert a continuous force between the rod member and the restraint elements. In one modification, two rod members have attached thereto a sheet of flexible material or fabric which acts as the restraint elements. Additional cable restraints can be employed joining the outer ends of adjacent rod members. The rod members are slightly bowed, and a bar member is secured centrally thereto in substantially chordal relationship. The stressing member rolls or slides on one bar member and pivots on the other. The stressing member is a slightly precambered one-piece rod or tube of spring material, carrying bifurcations at both of its ends to partially encompass the chord members, one bifurcation acting as a pivot and the other as a slide.