Cardfight!! Vanguard - Limit Break

This'll be brief, but here's a new concept I heard about, while some cards for Set 6 came out:

Limit Break: If you have number of damage in your Damage Zone, you can activate this ability. For example, if you have a Limit Break(4), you need 4 damage in your Damage Zone.

Sorry for it being brief, but it's a new concept you need to know for Set 6. Some examples will be posted in later posts.