You focus your attention on guarding your allies' backs.

Daily   ✦     Martial, Stance
Minor Action      Personal

Effect: You assume the stalwart guard stance. Until the stance ends, allies gain a +1 shield bonus to AC while adjacent to you. If you are using a shield, allies instead gain a +2 shield bonus to AC and Reflex while adjacent to you.

Published in Player's Handbook, page(s) 81, Class Compendium.