Breaking Block functions like a regular block, subject to all its limitations and requirements, but you also suffer a -4 penalty on the opposed roll. If you win the opposed roll, you block your opponent’s attack and inflict damage with your melee weapon or unarmed strike. Because of the impromptu nature of your blow, you may not apply Relative Degree to the damage. You may perform Breaking Block against melee attacks, only. In order to perform a Breaking Block, you must wield a weapon with which you are proficient. To perform a Breaking Block while unarmed, you must have the Improved Unarmed Strike feat.