A couple of years ago I bought a Lucet at a crafts show, had a go and and didn't get anywhere so put it away.  

I've just found sites which give pictorial instructions on how to use this ancient Icelandic cord-making device.  

This square, strong braid will not unravel on cutting and because of the way of making the braid very long threads can be used and length need not be predetermined.


http://www.lucets.com/pages/2color.html
http://www.pinterest.com/gbertholet/medieval-crafts-lucet/

... and a demonstration of its use: https://www.youtube.com/watch?v=3y5K7FiT2Og