The Block Replacer allows you to quickly replace blocks in the world with blocks stored in the item.
To store a block in the Replacer, right-click the block stack in your inventory onto the slot the Block Replacer is in, the same way you would use a Bundle.
You can empty the Replacer by right-clicking the Replacer stack onto an empty inventory slot.
Using the item on a block in the world will break that block and place a random stored block in its place.
Blocks with the block tag #irregular_implements:block_replacer_blacklist cannot be replaced with the Block Replacer.