IBS

From Diablo Wiki

More commonly called "fast block", Increased Blocking Speed helps characters block more frequently.

A character goes into block animation if its opponent succeeds in the hit check and the character succeeds in a blocking check. The character can do nothing else during the blocking animation. Blocking is only possible while engaged in melee combat, or while walking. (Not while running.) See the blocking article for more details.

Improvements to faster blocking are difficult to achieve since the bonuses to it are found almost exclusively on shields.

• In some cases the equipped weapon influences the blocking speed.
• The Assassin's Weapon Block skill is also affected by her Faster Block Rate, and the same values as for shield blocking apply.
• Act 3 mercenaries do not block even though they are capable of using a shield.
• In classic D2, this modifier was found only on Culwen's Point, and it had no effect.

(*) 1-handed swinging weapons include 1-handed axes, clubs, 1-handed maces, orbs, scepters, 1-handed swords, 2-handed swords wielded in one hand, throwing axes, and wands.