Page 58 - Derek E. Avery - The new encyclopedia of knots

taking the outside right strand across the inside right strand to the middle.

Then move the left side strand across the strand that became the new
inside right strand, to the middle. Now take the strand that has become
the new outside right strand across the inside right strand to the middle
(figure 32.1). This completes the first full sequence of movements, so that
you can repeat the process until you reach your required length of sennit
(figure 32.2).

figure 32.1

figure 32.2

Common sennit (seven-stranded): a more complex but more pleasing
version of the three-stranded common sennit, to which the same
principles apply.