You can keep you balance while walking on a tightrope, a narow beam, a ledge, or an uneven floor.

Check: You can walk on a precarious surface as a move-equivalent action. A successful check lets you move at half your speed along the surface for 1 round. A failure means that you can't move for 1 round. A failure by 5 or more means that you fall.

The difficulty varies with the surface, as well as the size and speed of the character attempting to keep their balance.

Surface                      DC

--------------------        ----
Uneven floor                 10
15 - 30 cm wide              10
 5 - 15 cm wide              15
Less than 5 cm wide          20
Larger than medium           +5 *
Smaller than medium          -5 *
Surface Angled               +5 **
Surface Slippery             +5 **

*Apply this bonus for every size class above or below medium.
**Cumulative;  if both apply, use both.

Being attacked while walking a tightrope: Attacks against you are made as if you were off balance. They gain a +2 attack bonus, and you lose your Dexterity bnus to Def, if any. If you have 5 or more ranks in Balance, then you can retain you Dexterity bonus to Def (if any) in the face of attacks. If you take damage, you must make a check again to stay on the tightrope.

Accelerated Movement: You can try to walk on a precarious surface more quickly than normal. If you accept a -5 penalty, you can move your full speed as a move-equivalent option. (Moving twice your speed in a round requires two checks.)

Reduced Movement: You can also try to walk on a precarious surface more carefully than normal, accepting a +5 penalty bonus and moving 1/4 of your full speed as a move-equivalent option.

Special: If you have 5 or more ranks in Tumble, you can get a +2 synergy bonus on Balance checks.