Back to Back (Feat)
Your ally's eyes are your own, and yours are his.
Prerequisites: Level 6, Perception 6 ranks
Benefit: While you are adjacent to an ally with this feat, you cannot be flanked.
Special: While adjacent to an ally with this feat, any time you make a melee to-hit roll against an enemy your ally does not threaten, you can a +1 circumstance bonus on that to-hit roll. This bonus applies to all such attacks, and there is no limit to how often you can get the bonus, as long as the conditions are met. The bonus cannot stack with itself. (The easiest way to get this bonus is for you and your ally to stand next to each other, while having enemies on opposite sides of both of you, and attacking the enemies that your ally cannot reach.)
Note: This is a Teamwork Feat, meaning it does nothing unless you and at least one other member of your party each possess this feat.