Reader Mike emailed in to ask us a question that we've long contemplated on the vagaries of Shields. Specifically, he was wondering why he and a warrior buddy both had different multipliers for block on their character window, but both blocked for approximately the same amount. Well, since I'm a prot warrior and therefore love shields and want to make little shield babies with them, I figured I'd provide some information.
Using a shield means you have to keep track of two separate stats. The first is Block Rating, which is the percentage multiplier on the character window: it tells you the chance for you to block an attack against a mob at your level. The various Block Rating on gear like the Battleworn Tuskguard or Bulwark of the Amani Empire (both pictured to the right) add to your chance to block an incoming attack the same way that Crit rating adds to your chance to crit or Defense rating adds to your ultimate Defense score. You can even see that the nice folks at Wowhead have done the math for us on how the rating converts to chance to block. Block rating, however, only tells you half of the story.