Locking System by Craziest

Imagine having a blue back card inside a clear plastic envelope closed with a padlock. Now your spectator chooses a card from a red deck and signs it. The magician loses the spectator's card through the middle of the deck. In a super magical way the blue card that was inside the envelope is the spectator's card!

Can you find an explanation? No one will find it!

You will receive everything ready to go:
- A clear plastic envelope.
- A padlock with your keys.
- A special trick card.
- Video-tutorial.