Another question about Newman's card cons

They don't tell you, they just want you to believe he could have somehow done it. That was the point of showing the card tricks in the scene before the card game.

In a normal game, no player would be comfortable letting another player take the cards off the table like that, and particularly holding them up against your body.

That is why Gondorf played up the fact that he was trying to hide his cards from Lonnigan's bodyguard who was sitting directly behind him. This gave him the opportunity to execute the sleight-of-hand switch.



Whose idea was it for the word "Lisp" to have an "S" in it?

This particular switch is not shown to us... but earlier in the game we see one of them being hinted when "Shaw" sneezes, wipes his nose with his tie and his left hand dips below the edge of the table. So we know he's up to cheating all along.

We also know that Henry has an entire deck of extra cards to use since J.J. gives him a "Tally-Ho Fan [and a] Tally-Ho Circle".

The poker game is played with red Tally-Ho Fan cards... and we see the such a deck neck to the ones Henry are showing off with to Johnny.

Curiously the blue cards that Henry is playing before Johnny with are blue Bicycle Rider, not Tally-Ho cards.

/J-Star

De gustibus non est disputandum

How he's able to do it falls within his rights as an expert card shark. We don't have to know, we just have to believe.