Minecraft wiki entry for Barrel, associated text: In Java Edition, a barrel can be "locked" by setting its Lock tag using the /data command. If a barrel's Lock tag is not blank, the barrel cannot be opened unless the player is holding an item with the same name as the Lock tag's text. For example, to lock a barrel at (0,64,0) so that the barrel cannot be opened unless the player is holding an item named "Barrel Key", use /data merge block 0 64 0 {Lock:"Barrel Key"}.