Blades Above and Below (Combat, Teamwork)Source Inner Sea Races pg. 201
You attack high and your ally attacks low, denying your foe the chance to dodge your attacks.
Prerequisites: Base attack bonus +6.
Benefit: When you and your ally who also has this feat threaten the same enemy, you’re both considered to be flanking that enemy, regardless of your actual positioning. To gain this benefit, you and your ally must be of different size categories, and your target must be the same size category as either you or your ally.