Lucet braiding
A lucet is a tool used in cordmaking or braiding that dates back to the Viking and Medieval periods, when it was used to create cords that were used on clothing, or to hang items from the belt. Lucet cord is square, strong, and slightly springy.
Lucet cord is formed by a series of loop like knots, and therefore will not unravel if cut. Unlike other braiding techniques such as kumihimo, finger-loop braiding or plaiting, where the threads are of a finite length, lucetted (or knitted) braids can be created without pre-measuring threads and so it is a technique suited for very long cords.
You can buy your own lucets here.
Find out how to lucet here. How to Lucet, by Evelyn Skae