Here’s a few variations on the I deck (If you have to ask what it is, this isn’t for you)
There are a few – who would rather keep it under their hat – but they switch the ID deck into play while handing the spectator a different coloured box and deck,
The volunteer is given their choice of red or blue. They are asked to shuffle. They hand their deck back. That are asked to shuffle the other deck. In the process the first deck is exchanged for the ID.
Then the volunteer is asked to hold the “original” deck (red or blue) and hand back the second deck.
From that point you’re open to having anyone pick a card from the second deck OR the volunteer names a card which is removed from the second deck (or whatever you want to do)
The point is that the supposedly shuffled ID is being held by the volunteer until the revelation.
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Yes it seems like a long description and work (I myself don’t bother doing it this way) BUT after the performance the spectators who try to reconstruct the effect rule-out trick decks because “it was shuffled”
The whole routine is reminiscent of Billy McCombs version of Himber rings, where you involve people sitting to the right and sitting to the left – so you can do what you need to do. It plays well, from the times I’ve seen it.
My clean-up is to say that I’ll explain just one. The cards (invisible) that I handed you were ALL the_________ so you had no choice. Now when I put the card away, there’s no need to cut the cards and put it on the bottom or do any other clean-up because that explanation allows you to put their card back where you found it, and you’re done.