Source: Player's Handbook
You are proficient with bucklers, small shields, and large shields.
Benefit: You can use a shield and suffer only the standard penalties (see Armor).
Special: Barbarians, bards, clerics, druids, fighters, paladins, and rangers automatically have Shield Proficiency as a bonus feat this feat. They need not select it.
Normal: When you are using a shield with which you are not proficient, you take the shield's armor check penalty on attack rolls and all skill checks that involve moving, including Ride checks.