Two jacks are sent into the deck to find a selected card. They do it by visibly rejecting half the deck and leaving just one card between them. Naturally, it is the right one.
Usually a sandwich effect suggests that somehow the two jacks (or whatever) penetrate through the deck to find the selected card. In this routine the idea is that the jacks are actually ejecting unwanted cards from the deck, leaving the selection in situ.
To perform, take the two black jacks out and place them face up on the table. Have any other card selected, remembered and returned to the pack. Control the selected card to the top of the deck. Place the deck on the table.
“Believe it or not, the two black jacks are going to find your card. But they need a little help from you. Would you cut about a third of the deck off and place it there.”
The spectator does what you say, placing the cut off portion to the side.
“Now pick up one of the jacks, either one, and drop it on top of the pile you just cut off.”
He does, and you ask him to cut off a second packet of cards from the deck, “about half this time,” and drop it on top of the jack he just handled, thus burying it.
“Great. Pick up the second jack and drop it on top.”
He picks the remaining jack up and places it on top of the pile of cards he has been building.”
“And then drop the rest of the cards on top.”
He does as you say and drops the remainder of the deck onto the face up jack. You square the deck, pick it up and recap what has happened as you spread the cards between your hands.
“What you’ve done is placed the two jacks in the middle of the deck. They are separated by what, about twenty or so cards?”
As you spread, the upper third of the deck you will come to the first jack. Spread past it but cull it under the spread until you come to the second jack. Because of the way you have handled the cards the second jack is directly above the selection. Load the culled jack below the selection as you close the spread, apparently having reshown the jacks to only emphasise how many cards separate them.
You are almost ready to finish. Turn the deck face up in the left hand. “I think that your card lies somewhere between the two jacks. All the jacks have to do is get rid of all the other cards. Watch!”
Click your right fingers and then execute the Self-Cutting Deck flourish from The Royal Road To Card Magic (Chapter Thirteen, Miscellaneous Flourishes).
Briefly, the left forefinger snaps inwards against the outer end of the deck, propelling the lower half towards you where it is caught by the waiting right hand. The instructions in the Royal Road show the right hand palm down as it catches the cards, but I like to have the hand palm up. It is already behind the deck when it clicks its fingers and opens to receive the ejected cards.
The effect is that a packet of cards suddenly and unexpectedly leaps from the deck. You catch it and immediately spread the cards in a fan face up on the table, asking the spectator, “Can you see your card there?”
He won’t. So you turn the remainder of the deck face down and spread it across the table to reveal the two face up black jacks, now separated by only one card. It is, of course, the selection.