In the Clinch
Most Practitioners use the the forward forearm with a rising elbow, for a purely defensive action. This arm action is seen in Wing Chun as well as other Karate Katas (Nai Han Chi Nidan as example) and many other Martial Styles. But it is almost always utilized as a defensive not as an offensive tool or leverage.
When this action is initiated from the hip, it has powerful leverage (fulcrum and lever), that is in turn a powerful offensive tool for in close fighting applications. These range from Striking to Grappling to Tuite, all stemming from the White Crane Fighting Styles.
For the first application, we use the Bon Sao's Leverage to incapacitate the opponent, This is accomplished with...
To learn the method, targets and see the affect in real time, the extended films are located at these links: