Tower Shield Proficiency
(Player's Handbook v.3.5, page 101, DnD 3.5)
[General]
You are proficient with tower shields.
Prerequisite
Benefit
You can use a tower shield and suffer only the standard penalties (see Table 7-6: Armor and Shields, page 123).
Special
Fighters automatically have Tower Shield Proficiency as a bonus feat. They need not select it.
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.