In Magic: The Gathering, a sideboard is a set of cards that is separate from a players primary deck and is used to customize a match strategy against an opponent by enabling a player to change the composition of the playing deck). A sideboard typically contains 15 cards and is used to supplement a decks weakness against certain opponent decks). During a match, players can swap cards between their main deck and sideboard to modify their deck against their opponent. The set of cards to include in a sideboard can affect the gameplay dynamics of a deck and can lack versatility because of the limited number of cards it can contain and the diversity of decks that can be constructed). The restrictions on the composition and use of a sideboard can be found in the deck construction rules for a particular format type.