Abstract: The invention relates to a double assembly system that can be used for pivoting, rotating or folding operations. The invention is suitable for use in the production of furniture or other construction elements and structures, for the purposes of folding and unfolding, opening and closing, and, depending on the spatial orientation thereof, for securing a part in its use position. The invention can be used to join generally planar parts. The invention is formed by a group of elements (1) which are interlocked with other elements and which, when joined, allow a rotational movement through a specific, pre-defined angle.