Null Tiles and Null Walls
Null tiles are a special type of tile added by the mod which are used to tell the generator "Hey, don't change whatever tile this would replace!". Whenever a structure with null tiles is generated, any existing tiles in the world, be it dirt, air, or an exotic modded tree, will remain exactly as it was before generating the structure. They're an essential tool to ensuring your structures blend into the world and don't cause unintended destruction.
Null tiles enable you to create non-rectangular structures by filling the negative space within the rectangular bounds of a structure with them. When generated, only the shape of your structure will be effected.
Using null tiles is simple, simply get the "Null Tile" item and place it as you would any other tile. The item has unlimited uses and can be placed faster than normal tiles. If you want to place both null tiles and null walls at the same time, you can use the Null Tile Place-O-Matic to do so.
Null walls mirror the behavior of null tiles, except for walls. When generated, a structure will still place walls exactly as they were, even when behind a null tile, unless a null wall is placed on that tile. The seperation of this functionality into tiles and walls allows you to create structures where the edges of walls wont stick out of the ground, or where you want to make sure an area of your structure contains no solid tiles but can still contain natural walls.
Null walls can be used in an identical way to null tiles, and both can be placed at the same time with the Null tile Place-O-Matic.
