In vanilla, you can pick-block (default Middle-Click). If you in creative mode and hold Ctrl while you pick-block a Block Entity (Chests, Hoppers, Droppers, Furnaces, Campfires, etc.) you get an item with the data associated with it (like what's in a chest). With this mod, if the block you ctrl + pick-block isn't a Block Entity then it will copy it's block state (the direction it's facing, if a redstone powered device is on/off, if a campfire is lit, if a block is water logged, etc). For example stairs: If you ctrl + pick-block an upside down, west facing stair, then no matter which way you're facing, it'll always be upside down, facing west.
