Enchanting Shields
Shields can be enchanted to increase their ability to block (call it Blocking Chance). The wielder of an enchanted shield can add Enchantment EL+1 to his shield skill for purposes of blocking. Since Shields have AV+User's EL for purposes of damaging the shield the Blocking Chance would be added to the User's EL for calculating whether a shield would take damage. A shield enchanted for both AV and for Blocking Chance be much less likely to be damaged or broken than the same type shield that wasn't enchanted.