Abstract: A puzzle consists of six or more elongated pieces. Each piece has a polygonal cross-section and a cavity whose dimensions are determined by the polygonal cross-section. The pieces can be arranged in two opposing groups of three or more pieces each, arranged substantially in parallel, and such that the cavity in each piece is filled by portions of other pieces as the groups are advanced toward each other. The pieces can be assembled and disassembled only in such a way that each piece is moved relative to others in a different direction to interlock the pieces in an assembled configuration, and no individual piece can be disengaged from the assembled configuration without disengaging all of the pieces.