Your masterful shieldwork provides even greater protection to your vital areas.
Benefit: Choose one type of shield (buckler, light, heavy, or tower shield) for which you possess the Shield Specialization feat. With the selected shield, you gain a +2 bonus to your Armor Class against critical hit confirmation rolls (this bonus stacks with that from Shield Specialization). In addition, once per day you may negate a critical hit, and damage is instead rolled normally.
Special: You can gain this feat multiple times. Its effects do not stack. Each time you take the feat, it applies to a new type of shield.
Advanced Player’s Guide. Copyright 2010, Paizo Publishing, LLC; Author: Jason Bulmahn.