You can make free attacks on foes that you knock down.

Prerequisites: Base Attack Bonus 6, Improved Combat Maneuver(Trip)

Benefit: The bonus to combat maneuver DCs increases by 2. You may increase the action of your combat maneuver attempt to full-round action. Doing so leaves your opponent in a very defenseless way until the start of your next turn. Every one who comes into threat range of this opponent may perform a single attack of opportunity versus that opponent.