Minecraft wiki entry for Block_entity_format, associated text: : The block entity's root tag.
 BaseX: The X postionn of its base.
 BaseY: The Y postionn of its base.
 BaseZ: The Z postionn of its base.
 Size: The size of this chalkboard.
 OnGround: True if it is on ground.
 Locked: True if it is on locked.
 Owner: The Unique ID of its owner.
 Text: The text on the chalkboard.