| Side Deck
A Side Deck (Japanese: サイドデッキ Saido Dekki) is a Deck of up to 15 cards, separate from the Main Deck and Extra Deck. The Side Deck is used in Matches between Duels, to alter the contents of the Main Deck and/or Extra Deck. A side Deck is not required, but can assist in duels against specific opponents.
- Before a Match starts, you must show your opponent your side deck the number of cards in it without revealing its contents. This is to let them know that you use one.
- If you are using sleeves for your side deck, they must match with the sleeves used for the Main or Extra Deck, depending on where it would begin during the duel should you use it during the duel.
- Side Decks can only be utilized AFTER the first round of a match.
- When using your side deck to alter the contents of your Main and Extra Deck, the number of cards in your Main and Extra must remain the same.
- At the end of a match, all cards that were moved between the Main and Side must return to their original registered areas.
Common Side Deck cards include various forms of Spell and Trap removal, such as "Dust Tornado" and cards that can directly counter common strategies, such as "Prohibition", "Chain Destruction" and "Royal Prison".
Since a Side Deck is not compulsory, a value of 0 for a Side Deck is considered legal. In both the OCG and the TCG, any value between 0 and 15 inclusive is permissible.
The Side Deck is invaluable in tournament play. Facing certain Decks can be a walk in the park or a nightmare depending on the contents of your Side Deck.
Previously, the Side Deck could not be used to alter the contents of the Extra Deck, though this has been changed. This is done to better suit a strategy against an opponent's Deck.