Karate with crown caps

They borrow a bottle cap or pick one up from the table. They hold it between their index finger and thumb – a scream – a blow :
> Your right index finger has pierced the crown cap!

It sits on the finger, can be removed and, if desired, given to a spectator as a souvenir of an impressive demonstration.

You know the drill: Shortly after midnight, it all starts: one person opens his beer bottle with a lighter, another with a well-aimed palm strike, a third has the right bite...
But : You have karate skills: you pierce the crown cap with your index finger and open the bottle!

2 tricks in one: Karate and Karate Revers.