The Butterfly Knives or Bart Cham Dao (eight slashing knives) are one of the highest skills in the Wing Tsun System. As a weapon, they are incredibly potent and vicious, and as a training tool, they take years to master.
Like the pole (Luk Dim Boon Kwun) the knives will help to train the wrist and grip. The Bart Cham Dao form will also introduce some very advanced footwork to the Wing Tsun technician. As well, many of the aspects and theories of the Bart Cham Dao form can be adapted for unarmed use.
At an advanced level practitioners will practice using the pole against the knives, and vice versa. Such training represents some of the highest levels of martial arts practice due to the extreme accuracy and control required of these difficult-to-master weapons.