Patent ID: 7640775

Claim:
A sheet of material formed for folding into a three-dimensional structure comprising: a sheet of material having edges and joinder structures proximate the edges formed to join the edges together; a plurality of shape-controlling folding structures formed in the sheet of material along a plurality of desired fold lines, the folding structures being positioned to enable folding of the sheet of material into a three-dimensional structure of desired shape, and the shape-controlling folding structures being configured to cause the joinder structures to be positioned together in registration for joining when the sheet of material is folded; at least one retention structure formed in the sheet of material to retain the joinder structures and edges together, the retention structure being provided by retention folding structures formed for folding of the sheet of material along a retention fold line positioned proximate the free edges producing folding of the sheet of material out of the common plane; and a keeper assembly provided by at least one projection in an edge of the sheet of material and a mating opening dimensioned to receive the projection and oriented to prevent unfolding of the sheet of material along the retention fold lines, wherein the joinder structures are formed in free edges and are adapted to interlock the free edges against separation and are provided by mating dovetail structures in the free edges, the dovetail structures interlocking the edges in a common plane, and wherein the shape-controlling folding structures and the retention folding structures are slits that define a plurality of spaced-apart folding straps having center lines extending obliciuely across the desired retention fold line.