In VT vs VT : Your partner attacks your position (left man, right wu) with a left jut and a right vertical punch. He enters square on yet diagonally in an attempt to cut you off. You, however, are no chump and the second you feel his jut against your left man sau hand you pull it back. At the same time, your right wu sau hand (always having forward intention) is itself converted to a vertical punch which, together with your own "entering" footwork, cuts off your partners punch travelling from the "inside out" (concept tan sau). You are thus able to defend and counter-attack simultaneously, not chasing his arm but attacking the center (his head).