Hello!

If you are talking about this item (check the image below), then this item isn't usable yet at this moment. This item is meant to be used for exchanging Skill Breakthrough Books through the Tsunade NPC which isn't yet activated or implemented on the game. On the other hand, if you are talking about the Secret Scroll Plate or Plate Fragment then it is for opening another Set of Stats for the Secret Scroll Feature, just like what Aika said above. Thank you.