A walk in the pattern is a combination of scrambled sAiBcA and B (iBcBsA). This is a combination that was deemed “impossible” because both manipulators interact with B on beat 2 and with A on beat 3.
In practise, this leads to a very nice walking motion: On beat 1, the B manipulator intercepts the pass from A to B and the Saibca manipulator substitutes from B to a (handback). No interaction so far…
On beat 2, the Saibca manipulator intercepts a self of B (and becomes B). So, the B manipulator who intercepted the pass on beat 1 stays manipulating. He can´t turn out and become B as he is again intercepted on beat 2. The B manipulator leads the (new) Saibca manipulator towards their common goal: A, giving him another club. Arriving at A, the Saibca manipulator performs his beat 3 action: carry to A. Then, he immediately intercepts the pass from (just turned) A to B (but, of course, does not become B), he becomes the new B manipulator. The B manipulator does not perform his beat 3 action (sA) as A is getting a carry from the other manipulator.