Abstract: A generally rectangular game board block has a recessed arcuate part formed in a first end, and a protruding arcuate part formed in a second end. The arcuate parts share a common radius of curvature. In one embodiment, the complemental arcuate parts of contiguous game board blocks abut one another so that they are pivotal with respect to one another. In another embodiment, a retainer associated with the recessed arcuate part engages a rim of the protruding part of a contiguous game block so that the contiguous parts are positively held together as they are rotated with respect to one another. Another embodiment has a hinge-like interconnection and a bias member introduces play into the structure.