If you’re serious about collecting or playing Pokémon cards, you’ve probably heard the term “double sleeving.” While it may sound like overkill to beginners, experienced collectors and competitive players know that double sleeving is one of the best ways to preserve card quality and maintain long-term value. Humidity and accidental spills are major threats to cards. Double sleeving creates a tighter seal, reducing the chances of liquid reaching the card itself.