Dwarven Armor Proficiency( Races of Stone, p. 138)
You are familiar with exotic armor of dwarven manufacture and understand how to use it properly.
Armor Profi ciency (heavy), Dwarf,
You are proficient with battle plate, interlocking plate, interlocking scale, and mountain plate, and you take no armor nonprofi ciency penalties when you wear any of these types of exotic armor. (See Chapter 7 for descriptions of these armor types.) NORMAL: A character who wears exotic armor with which she is not proficient takes its armor check penalty on attack rolls and on all Strength- and Dexterity-based skill checks.
A fighter may select Dwarven Armor Proficiency as one of her fi ghter bonus feats (see page 38 of the Player's Handbook).