How to Lock or Unlock an SD Card on Nintendo 3DS Family
Nintendo 3DS
In this article, you'll learn how to adjust write-protection for an SD Card.
Note: microSD cards are not lockable.
What to do
Set the lock slider to locked or unlocked.

- The down position will enable write-protection, locking the card.
- The up position will unlock the card, enabling you to save and erase data on the card.