Step 1

Standard Vert Stack formation, "option" called

Step 2

Front of stack (3) makes a cut in to forced side and then cuts out and deep hard, ideally drawing the mark from the back of the stack (7) with him

Step 3

The out-cut from the front of the stack, as described, and defence 7 goes with

Step 4

With his mark gone, 7 is free to cut in along the break side