Balance

Balance (Dex; Armor Check Penalty) 

Check
You can walk on a precarious surface. A successful check lets you move at half your speed along the surface for 1 round. A failure by 4 or less means you can’t move for 1 round. A failure by 5 or more means you fall. The difficulty varies with the surface, as follows:

Being Attacked while Balancing
You are considered flat-footed while balancing, since you can’t move to avoid a blow, and thus you lose your Dexterity bonus to AC (if any). If you have 5 or more ranks in Balance, you aren’t considered flat-footed while balancing. If you take damage while balancing, you must make another Balance check against the same DC to remain standing.

Accelerated Movement
You can try to walk across a precarious surface more quickly than normal. If you accept a -5 penalty, you can move your full speed as a move action. (Moving twice your speed in a round requires two Balance checks, one for each move action used.) You may also accept this penalty in order to charge across a precarious surface; charging requires one Balance check for each multiple of your speed (or fraction thereof) that you charge.

See also: epic usages of Balance.

Action
None. A Balance check doesn’t require an action; it is made as part of another action or as a reaction to a situation.

Special
If you have the Agile feat, you get a +2 bonus on Balance checks.

Synergy
If you have 5 or more ranks in Tumble, you get a +2 bonus on Balance checks.