Step 1

Initial box setup. The other 'handler' (2) can often be a cutter since they are the one person who will definitely not be coming under for a pass.

Step 2

Other person back (2) initiates activity by cutting towards either of the two cutter positions (3 and 4).

Step 3

With 2 initiating straight up towards 4, 4 cuts deep and 3 comes under to the open space. 4 must make the deep cut a viable one - it's not just a clear out.

Step 4

IF there is no pass completed, cycling continues...

Step 5

...

Step 6

IF the initial undercut by 3 received the pass, then 1 is the initiator and determines the next flow of the box. (Although note that sometimes after the initial connection, it's okay for the box setup to breakdown in favour of opportunity and continuation cuts.)

Step 7

RESET to initial box.

Step 8

If other handler back initiates by cutting towards the other position (3)...

Step 9

... then the cycling of the box just moves in the opposite direction.