A sheet of material formed for folding into a three-dimensional structure. The sheet has edges formed with joinder structures, such as dovetails, and a plurality of folding structures, such as slits, grooves or displacements, that control folding of the sheet in a manner causing the joinder structures to be folded into interlocking interengagement. The folding structures are configured for very precise folding of the sheet so that the folding structures will be in precise registered juxtaposition. Additionally, the sheet of material includes a retention structure, such as a retention fold or a retention deformation, which will prevent unfolding of the sheet. A method for fastener-free joining of sheet edges together also is disclosed, as are the resulting three-dimensional structures.