A playing card, a key, a coin, or even a borrowed credit card melts through a solid deck!
After performing a card trick with a regular deck, without any swapping, you offer to show an amazing optical illusion. You borrow a key, a credit card, a driver's license, etc., and make the object melt through your solid deck.
Once the illusion is revealed, you can show each card in the deck, one by one, and the audience can see that the cards are real and have no holes.
The mechanism is easy to put in and take out of the deck, allowing you to hand it over for examination if you wish, or continue with other effects using the same deck.
Easy to build.
Fun to perform.