JKD is based on simplicity.  In its
design, it utilizes relatively few
techniques.   
Essentially there are a total of five punches. 
Though they are few, each one can be performed with a number of variations, to fit the need at hand.   
To expand on some of those
variations, the Hook Punch can be broken down into separate
applications. 
Although they vary drastically in their mechanics, they are all
classified as hooks because they achieve comparable results using similar  motion.     
Hooking punches serve many needs.  They may, at close range, knock an enemy flat.  They may also be used at longer range as a counter that lands when least
expected.  Hooks add new
angles to the attack.  They may score, when a straight punch may not.

The Loose Hook

The Tight Hook

The Shovel Hook

Corkscrew Hook

All the hooks explained here are performed with the lead hand.  This is not to say that rear hooks may not be
employed as well.
Hooking from the rear can be very effective in many situations.   Check back for futher information on these and other techniques.