Typically practiced as follows One practitioner executes continuous center-line punches while the other (the one controlling the routine) executes random blocks and punches but with intermittent Tan Sao Stops to where both parties then fight for center line position until the controller releases the opponents lower held write to where the opponent should then immediately continue punching and repeat until one or both practitioner’s shoulders become burnt-out. It’s important to understand that both parties continue to apply pressure on their shoulders. For example, when the defensive practitioner (controller) stops at Tan Sao, both parties begin fighting for center line position. At the same time, the offensive practitioners throwing the continuous punches attempts to continue throwing the punches with the arm that would be used for the next but, however, he cannot do so due to the controller holding his lower wrist. But he still continues to try by breaking the wrist-hold and punching. In other words, no matter who is offense or defense, both parties receive the full shoulder workout, only that one party practices straight punching (which in Wing Chun can be looked at as a jab in boxing, though never telegraphed), while the other practices arm control and reacting to the straight punches using random moves – whatever comes to mind, and which is looked simply as a drill that sharpens your blades. Rotate offense/defense between practitioners. Note - In this example you can see the student’s form degrading as his shoulders become exhausted. Don’t sacrifice form for strength. Try to maintain the form of the punches, Tan Sao blocks, or any other moves executed during the drill. Don’t continue to practice moves that are out of form. When it gets to that point, you’ve become fully spent and should then stop and recover your strength before continuing on.