Armored Sacrifice (Ex)Source Armor Master's Handbook pg. 15
When damage would cause the fighter or an adjacent ally to be knocked unconscious or killed, the fighter can instead direct the damage to a suit of armor that he is wearing or a shield he is using as an immediate action. The original target takes no damage, but the armor or shield is treated as if it had only half its normal hardness. The fighter can use this option once per day, plus one additional time each day at 11th level and every 8 fighter levels thereafter, to a maximum of three times per day at 19th level.