hi sao (chi shou, sticking arms) is one of the most famed aspects of wing chun kuen. Like san sao, sticking arms is a dynamic and ever-changing laboratory through which wing chun kuen techniques are deconstructed and explored in application. Chi sao, however, focuses this exploration on the development of the reflexes used when the bridges are already in contact. At this extremely close range, eyesight can sometimes be too slow to adapt to a fast opponent and feeling and reflex becomes paramount.

There is a saying in wing chun kuen that "sticking arms is like asking the way." In this sense, every wing chun kuen bridge is really a question posed to the opponent. If they do not respond, they can be struck. If they do, the bridge will change (based on feeling) and ask again. Thus, it is actually the opponent who sets up his or her own defeat.

Sticking arms begins with simple drills and exercises, such as the double circling arms, rolling wings, and the famed luk sao (rolling arms). At first, partners work to develop and maintain their body structure and sense defects in others. Later, changes are introduced and the openings they find exploited. This continues until the drill becomes a free-flowing exchange of techniques, with the bridges simply joining and going from there.