Outside of a pure boxing match, every singled fight you get in.
Think about how often Boxers clinch up and lock up with each other.... in a REAL fight, you won't have a ref to save you or break the clinch up. All of that is grappling. Just having a bit of know how can put you so far ahead of people that don't, its ridiculous
My last street fight ended in one punch and me in jail for the day. There was no clinching involved.