Minecraft wiki entry for Dropper, associated text: A dropper can be "locked" (or subsequently unlocked) by setting the dropper's Lock tag with the /data command. If a dropper's Lock tag is not blank, the dropper cannot be accessed except by players holding an item with the same name as the Lock tag's text. For example, to lock a dropper at (0,64,0) so that only players holding an item named "Alice's Key" can access the dropper, use /data merge block 0 64 0 {Lock:"Alice's Key"}.‌[Java Edition only]