You use your shield like a wall of steel and wood. When an opponent attempts to draw in close to you, your shield forces him away or ruins his attacks.
Prerequisites: Shield Proficiency, Shield Specialization.
Benefit: You apply your shield bonus to your touch AC, and on checks or rolls to resist bull rush, disarm, grapple, overrun, and trip attempts against you.
Special: A fighter can select Shield Ward as one of his fighter bonus feats.
Source: Player’s Handbook II, page 82.