The magician spreads the deck of cards to prove that there is no gimmick. Borrows two quarters and a clear glass from the audience. The glass is placed on top of the deck.
The magician takes one coin, and slams it to the glass. The coin magically penetrates the glass!
The magician takes the other coin, and slams it to the glass. The coin once again penetrates the glass!
Takes the glass and gives the two coins back to the audience. Spreads the deck of cards again to show that nothing is wrong.