[1][2] It was made famous by Chinese folk hero Wong Fei-hung, who is reputed to have used it to great effect.
Frequently it is presented as a simple but blindingly fast kick, in which the upper body, head and arms remain stationary whilst the kick is performed leaving the opponent unaware of the incoming strike until after it has been performed.
[4] In practice it consists of a simultaneous grapple or distraction with the hands and a low kick.
[5] The combination of the low target area of the kick, the close range of the strike (which should be conducted from within hand strike / grapple range) and the use of diversionary technique lends it the appearance of supreme speed which the technique has become famous for.
[6] It is also the key component to learning how to perform a double or even triple strike consistently, surprising your opponent with its power and effect.