Plug is a blackjack dealing term tied to the plastic cut cards used in multi-deck games. When six or eight decks are loaded into a shoe, one cut card is placed towards the back to mark where dealing stops and the next shuffle begins, and another keeps the discards apart from the cards still to be dealt. The section of cards fenced off in this way is the plug. Because it is never dealt, it hides the last cards from view and limits the information available to card counters.
Where the cut card sits sets the penetration of the shoe, the share of cards dealt before a reshuffle. Deeper penetration means fewer shuffles but helps card counting; shallower penetration does the opposite. Many RNG blackjack games reshuffle the virtual deck after every round, while live dealer tables follow their studio’s shoe procedures, which operators should review alongside the game rules.