You can use your weapons to protect you as well as armor does.
Benefit: When you are not flat-footed, wearing light armor or no armor, and have a melee weapon you have Weapon Focus for in hand ready for use, you gain an armor bonus to your AC. This bonus is equal to 1/2 your character level +2. Any circumstance that would cause you to lose your dodge bonus also causes you to lose this armor bonus to AC. Like any armor bonus, it does not stack with other sources of armor.