Official substitute cards are used to represent double-faced cards in sets that contain them. Only official substitute cards may be used to represent double-faced cards in a deck.
It is a player’s responsibility to have substitute cards or appropriate sleeves. A judge should not create proxies to represent substitute cards unless the original card has become damaged during the current tournament.
The name of the card that the substitute card is representing must be legible. Other modifications must follow the rules for modifying normal Magic cards.
Substitute cards represent cards, and cards have to have their name displayed clearly on them. There is space on these cards for other alterations, and do you know what happens to a substitute card that doesn’t follow the rules for modifying the card? The same thing that happens to everything else.
The use of substitute cards is required if a player has double-faced cards in their deck and is not using completely opaque sleeves.
The easiest way to check for a sleeves opaqueness is to look for the white mana symbol on the back of a non-double-faced card.
If a player uses a substitute card to represent a double-faced card in their deck, then all copies of that double-faced card in the deck must be represented by substitute cards, and any copies of that double-faced card in a hidden zone are considered to not exist for purposes of determining deck legality.
If a player accidentally shuffles their double-faced card into their deck with substitute cards, we treat them the same way we would a token shuffled in and remove them without issuing an infraction. Note that this also means you may not mix and match. If a player has Archangel Avacyn substitute cards in their deck, then they may also have Duskwatch Recruiter cards.
Each individual checklist card used must have one (and only one) of the items checked.
Checklist cards are substitute cards from early sets that had checkboxes for specific cards. You didn’t have to write the name, you just checked a box. Some players will black out all of the boxes except for the card they are representing. Any way of marking the checklist card that makes the card unambiguous is acceptable.
A substitute card is only used while the card it represents is in a hidden zone. The card represented by a helper card is not a playable Magic card until the substitute card has been placed in a public zone. Multiple substitutes cannot be used to represent a single copy of the actual card. For each substitute card used, the player must have a copy of the actual card available, though they are not considered sideboard cards and are not presented to their opponent.
When the card is on the battlefield, the real card should be placed over the substitute card. Checking to make sure a player has the proper number of double-faced cards for the number of substitutes in their deck is very important during deck checks. Also, you can’t have one physical copy of a DFC and use four substitute cards for it in your deck.