Editing Ogre:CharacterCodex:Combat (section)

===Nonlethal Damage===
Certain attacks deal nonlethal damage. Other effects, such as heat or being exhausted, also deal nonlethal damage. When you take nonlethal damage, it only damage your hit points, but never your Constitution ability.

Nonlethal Damage with a Weapon that Deals Lethal Damage: You can use a melee weapon that deals lethal damage to deal nonlethal damage instead, but you take a –4 penalty on your attack roll.

Lethal Damage with a Weapon that Deals Nonlethal Damage: You can use a weapon that deals nonlethal damage, including an unarmed strike, to deal lethal damage instead, but you take a –4 penalty on your attack roll.