Abstract: A modular bottle closure comprises one or more exterior surfaces defining a hollow interior, a plurality of spaced engagement elements outwardly protruding from the exterior surfaces, a bottle cap interface element formed within the interior, and a coupling section coinciding with, or recessed from, a terminal edge of the closure. The coupling section frictionally engages engagement elements of another closure, whereby to couple together one or more closures. The plurality of engagement elements, which may protrude from the upper surface, are arranged by regions. A side of each engagement element of a region defines a locus of contact surfaces of substantially equal shape and length as the perimeter of the selected coupling section portion.

Abstract: A modular bottle closure comprises one or more exterior surfaces (2,6) defining a hollow interior, a plurality of spaced engagement elements (4) outwardly protruding from the exterior surfaces, a bottle cap interface element (8A) formed within the interior, and a coupling section (21) coinciding with, or recessed from, a terminal edge of the closure. The coupling section frictionally engages engagement elements of another closure, whereby to couple together one or more closures. The plurality of engagement elements, which may protrude from the upper surface (2) or from a sidewall (6) of the closure, are arranged by regions. A side of each engagement element of a region defines a locus of contact surfaces of substantially equal shape and length as the perimeter of the selected coupling section portion. As a desired construction system can be assembled from a plurality of closures, users will be encouraged not to discard the bottle closures, thereby providing an ecological benefit.