You are skilled at protecting yourself and your allies with your shield.
Benefit: When you use the total defense action while using a light, heavy, or tower shield, you can provide a cover bonus to AC against all attacks to an adjacent ally your size or smaller. This cover bonus is equal to your shield’s shield bonus and lasts until the beginning of your next turn. your shield does not provide a cover bonus to reflex saves.
Advanced Player’s Guide. Copyright 2010, Paizo Publishing, LLC; Author: Jason Bulmahn.