You are proficient with tower shields.
Prerequisite: Shield Proficiency.
Benefit: You can use a tower shield and suffer only the standard penalties (see the Armor and Shields table).
Normal: A character who is using a shield with which he or she is not proficient takes the shield’s armor check penalty on attack rolls and on all skill checks that involve moving, including Ride.
Special: Fighters automatically have Tower Shield Proficiency as a bonus feat. They need not select it.
Source: Player’s Handbook (version 3.5), page 101.