David Blaine Card In Window Trick
Effect : The performer asks the spectator to pick a card without him seeing the face and replace it in the pack.
The pack is then shuffled and the performer is apparently unsuccessful in locating the card.
After a few attempts, the cards are thrown against a window in a fit of rage. On looking at the window, the chosen card is seen to be sticking to it, even more surprising is
You will need two identical packs of cards and a willing helper.
The spectator is asked to choose a card from a pack, memorize it and without showing you, replace the card in the pack.
The pack is then shuffled and and a couple of attempts at "is this your card " tried followed by a look of disbelief when the spectator tells you that it is not their card (this is all part of the magic act as you don''t even need to know the card).
After a few attempts you fake an angry outburst and making sure the cards are squared up throw the pack broadside at the window, where they will hit the window and fall to the ground, except the chosen card which is sticking to the window.
Your helper was already positioned behind the window and spectator and had an identical pack of cards. He was able to see the chosen card and took the duplicate from his pack.
A small piece of looped sticky tape or magicians wax was attached to the duplicate card and it was stuck to the inside of the window.
The helper should then have walked away from the window the fact that the card is on the inside of the window. Here is one explanation of the trick.