This is really long but if you are Bruce Lee fan it's pretty interesting to watch.
The above footage is of Lee training with his senior Jeet Kune Do student Taky Kimura (who still teaches in the Seattle area). They are using a Wing Chun drill known as Chi Sao or "Sticky Hands" that develops trapping skills and the practitioners sensitivity of his opponents movement.
It may be hard to read on the film but essentially the two start with their wrists touching and take turns trying to attack the center line of the opponent, while the other tries to "trap" the attack by diverting the others energy or locking them up all the while maintaining contact. At about 3:15 you see Bruce Lee turn his head and do the drill with out looking.
Do yourself a favor and turn down the music. Lame.