Tunnel Fighting

Base attack bonus +1,

You do not take a penalty on your attack rolls or to Armor Class when squeezing into or through a tight space.

Each movement into or through a narrow space counts as if it were 2 squares, and while squeezed in a narrow space a character takes a -4 penalty on attack rolls and a -4 penalty to AC. See page 148 of the Player’s Handbook for more information on squeezing through tight spaces.

A fighter may select Tunnel Fighting as one of his fighter bonus feats (see page 38 of the Player’s Handbook).

You are adept at maneuvering and fighting in tight spaces and underground passages.