In brief, a pair of monkeys can hook around each other in more than eighty different ways, forming quite stable links. The links may be either symmetrical or asymmetrical. Repetition of an asymmetric link generates a helix. A symmetric link is self-limiting, so that the structure cannot grow further unless a new link is used to join symmetric pairs. It is possible to generate structures with point, line, 2D or 3D symmetry by choosing two or three different links (from the 80 or more possibilities) and repeating them systematically. An enormous number of compatible combinations can be found by trial and error. Many are shown in the sources quoted above.