Perfect BalanceAcrobatics Utility 6
No matter how narrow the path, you have the balance and coordination needed to walk it.
At-Will
Move Action Personal
Effect: You move your speed - 2. During this movement, you ignore difficult terrain, and you can move across any horizontal surface that is at least 3 inches wide without making an Acrobatics check.
Published in Player's Handbook 3, page(s) 164.