You can bolster a trained ally's defenses by interposing your own armored body.

Benefit(s): If you are wearing medium or heavy armor and are adjacent to an ally who also has this feat, as a free action, you may give your ally a circumstance bonus to her AC equal to half the armor bonus provided by your armor. This bonus lasts for 1 round. During this round, you gain no bonus to your AC from your armor.