You follow a powerful blow from your weapon with an opportunistic bash from your shield.
Prerequisites: Improved Shield Bash, Shield Master, Two-Weapon Fighting, base attack bonus +11.
Benefit: Whenever you score a critical hit with a melee weapon, you can make a shield bash attack against the same target using the same bonus as a free action.
Section 15: Copyright Notice
Advanced Player’s Guide. Copyright 2010, Paizo Publishing, LLC; Author: Jason Bulmahn.