Null Blocks are used in preparation for exporting a dungeon.
Null Blocks when placed can be harvested by hand, and will drop itself.
Due to these blocks being replaced on generation, they are impossible to obtain in survival.
Null blocks are ignored space in loaded schematics. This allows for blocks in the original location to not be overridden by the scematic itself.
Null blocks help with creating smooth transitions between the terrain and the structure itself, and generally should be used often.
- In Minecraft 1.10, a block of similar function called Structure Void was added to be used with Structure Blocks.