403.1. In certain competitions, players may have a group of additional cards (outside of their starting configuration) called a sideboard. See 600 for more information on sideboards based on competition formats.
403.2. Sideboard size and contents are dictated by the competition format.
403.3. Limits on copies of named cards as defined by competition format apply to the combination of Main Deck and sideboard.
403.4. Players may use sideboard cards to modify their deck in between games of a match.
403.5. Players may use those cards to modify their deck after the first game of a match.
403.6. Players may count the cards in their opponents’ sideboards at any time.
403.7. A player may look at their own sideboard at any time, but must keep it distinguishable from other cards.
403.8. A player’s deck and sideboard must be returned to their registered states before the first game of the next match.
403.9. If a match skips the first game due to a penalty or an intentional draw, neither player qualifies for