Abstract: A polygonal element has at each of its sides a coupling device designed to connect said element with an identical or different polygonal element equipped with a complementary coupling device in such a manner as to form a polyhedral spatial structure with a plurality of polygonal elements of this type. In accordance with the invention the coupling device comprises along each side of a polygonal element at least one female recess and at least one male projection complementary to at least one coupling device of other polygonal elements. Each recess has on at least one side parallel to the direction of penetration of the projection of a complementary coupling device an elastically yielding undercut and the projection has an undercut complementary to the recess. The undercuts are aligned together on a common axis so as to permit reciprocal rotation of the two coupled polygonal elements together.