  We describe a geometrical property of helical structures and show how it
accounts for the early art of ropemaking. Helices have a maximum number of
rotations that can be added to them -- and it is shown that this is a
geometrical feature, not a material property. This geometrical insight explains
why nearly identically appearing ropes can be made from very different
materials and it is also the reason behind the unyielding nature of ropes. The
maximally rotated strands behave as zero-twist structures. Under strain they
neither rotate one or the other way. The necessity for the rope to be stretched
while being laid, known from Egyptian tomb scenes, follows straightforwardly,
as does the function of the top, an old tool for laying ropes.
