Permanently enchant a shield to give 15 block rating. Requires a level 35 or higher item.
At level 70, you gain 1% to your Block Chance for every 7.884614944458 points of Block Rating. Therefore, with this enchant a shield will block attacks 1.9% more than without. It is helpful in reaching 102.4% avoidance for uncrushability, where as the popular alternative of +stam would be prefered if the tank is already uncrushable.
When an attack is Blocked, it does not necessarily mean that the target takes no damage. A Block attack-result inflicts the same damage as a normal hit, but reduced by an amount "X" that's based on the Block value and Strength of the target, as follows:
X = [(Shield block value) + ((Strength / 20) - 1)].
This enchant is often confused with Enchant Shield - Tough Shield - which adds + 18 block value. They are not the same thing. That enchant increased the amount of damage a shield absorbs when it blocks by 18, this enchant increase the chance to block by 1.9%.