Screwed Deck is a routine developed by Paul Harris in which the magician two halves of a deck are "screwed" together like a pool cue.
The first version published in Close-Up Kinda Guy (1983), with the manufacturing technique devised and described by Leo Behnke, was more of a gag. The magician at the end of an act, would unscrew his cards (in the case) and put them away in a box (ala a pool cue).
A similar idea by Harris was Unhinged published in Close-up Seductions (1984) in which the screw was replaced by a hinge on the card case allowing you to "fold" the deck in two. It was self-contained and got rid of the need for a deck switch.
In the early 1990s, a marketed version of 'Screwed Deck' came out using the principles of Unhinged but added kicker that the deck came out of the deck in a weird state (half up and half down). It starts out with the deck in two halves and are then screwed together. The deck does not screw all the way in (one half is face up and the other is face down). The deck of cards are slid out of the case and with one more twist and the deck becomes normal.
Next, "Improvised Screwed Deck" was published in the January 1993 issue of Magic Magazine in which the deck could be improvised quickly (without the case). A deck is twisted so that one end is face up with the other face down and then restored. Sort of a full deck Card Warp. A revised version of this "Improvised Screwed Deck" was published in Art of Astonishment Vol 3 page 66 (1996).
Paul's latest version called "Truly Screwed" was released on DVD #7 in the True Astonishment series.