As Edward stated in another thread, what else can you say about Trapping? There's plenty more that can be discussed regarding Trapping beyond simply training it. For example...
As little appreciated trapping is from the stand up, hardly anyone discusses trapping on the ground. And when they do, it's usually shown while one person is mounted and the other is on his back... he's using trapping to redirect punches / elbows and punching back... following up to some sort of grab / choke.
However, the real gem of trapping on the ground comes into play when your the guy on top. Now I understand why some people may not demonstrate it this way due to potential liability issues; however, as martial artists we should look into all aspects of combat.
From this position, you know that the guy can't back away from you. You also know that he is going to try to defend himself in some manner; with one of the most common methods being to "block". When this block occurs, it's a picture perfect opportunity for trapping to be incorporated. Trapping is one of the best ways to shift around the arms and eventually land the attack. The sensitivity gained by training trapping translates directly into this application. (And by Trapping, I mean the total application, not just the pinning.)
I've shown this (in quick demo form) to several people only interested in grappling and their eyes nearly buldge out of their heads wondering why they've never seen such previously.
Cory Smith
Jeet Kune Do Kali Association - Co-Founder
Fighting Method University - Chief Instructor