Four Jacks break into a house. One searches the basement, one the ground floor, one the bedrooms, one keeps watch on the roof. The police arrive, the lookout signals — and all four are found together, on top of the deck.
This is usually the first trick anybody learns, and it is still good. It is a story with a deck of cards as the illustration, which makes it the easiest trick here to perform for children and the hardest to perform badly.
How to perform it
Before you start, put three indifferent cards on top of the deck. Then the four Jacks on top of those? No — the other way round, and this is the one thing that matters. See below.
Set it so the top seven cards are: three strangers, then the four Jacks... reversed. Working from the top of the face-down deck: Jack, Jack, Jack, Jack is what you want left at the end, so the three strangers must be the cards you deal off first. Put the four Jacks on top, then the three strangers on top of them.
Fan the top seven as though showing four. Hold them so the three strangers hide behind the Jacks and only four faces are visible. Show them casually — this is not a display, it is a story prop.
Square them up and put the packet on top of the deck. You have just placed seven cards while saying four.
Deal the top three cards into the deck, one per "floor". One into the bottom third, one into the middle, one near the top. Those are the three strangers. The audience believes they are Jacks.
The fourth Jack is the lookout — leave it on top. Except all four are on top, together, which is the point.
Turn over the top four. Four Jacks, reunited on the roof.
Why it works
Because you showed four cards and placed seven.
Everything after that is storytelling. The three cards travelling into the deck are strangers nobody ever saw the face of, and the Jacks never move at all.
The one ordering mistake that ruins it.
The three hidden cards must sit above the Jacks in the packet, not behind them in the fan. Get it backwards and the cards you push into the deck are the Jacks themselves, and you turn over the top four to find three strangers and a Jack. It is the only way this trick fails, and it fails completely.
Checked in code: with the strangers above, the four Jacks are still together on top after all three are buried.
Making it play
Tell it as a story, slowly. The method takes fifteen seconds. The story should take a minute. That ratio is the trick.
Name the floors as you deal. "Basement. Ground floor. Bedrooms." A rhythm makes the three cards feel like three destinations rather than three cards.
Do not show the faces as you bury them. There is never a reason to, and a routine that never invites the question does not have to answer it.
More
All of these, with the ones you can deal through on screen, are on the
self-working card tricks page.