Abstract: A ground-based portable and collapsible structure comprises two similar rectangular plates hinged together and disposed in downwardly-diverging relationship with their hinge-remote edges engaging the bottoms of re-entrant slots opening from the upper edges of spaced and parallel bar means of inverted T-section disposed on the ground transverse to said plate edges. Each bar means may be an inverted T-section bar or two L-section bars secured to one another with their vertical webs mutually opposite and spaced, preferably by spindles on which spiked metal strips are mounted for pivotal movement between a first position wherein it is accommodated in said gap and a second position wherein it projects downwardly from the L-section bars, the two strips being offset one to each side of the median plane bisecting said gap and being maintained in such dispositions by spacers mounted on the spindles alongside the strips.