/dev/null

The /dev/null is a tool added by. This tool is used to discard all of a single item type when they are picked up. It has a single inventory slot, which can be accessed through sneak-using it when not targeting anything; it cannot be in reach of another block. The item that is put in there is the "filter" item. Once the stack in that slot is full, all exact items will be immediately discarded on pick-up.

With a block in its slot, the tool can be used to place the block.

You can put a /dev/null inside of another /dev/null. Doing this 4 or 5 times will give you the advancement 'Stack Overflow'.