25% increased Defences from Equipped Shield
10% increased Physical Attack Damage while holding a Shield
Attack Skills deal 10% increased Damage with Ailments while holding a Shield 
Solidity is a notable passive skill that grants additional chance to block with a shield equipped. It also grants increased melee damage while holding a shield and increased defenses from equipped shields. Defences include armour rating, evasion rating, and energy shield.
- Mark_GGG (March 13, 2013). "Increased Shield Defenses?". Official Path of Exile Forums. Retrieved July 19, 2013.