How does Minecraft detect where it is placing a block?

[xxKobalxx]

How does Minecraft detect where it is placing a block?

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Im trying to work on multiblock placement, all in single space, but i cant figure it out, any suggestions?

[Draco18s]

Block.onAdded(...) //called any time the block is placed into the world for any reason, including block updates and being pushed by pistons.

or

Block.onBlockPlaced(...) //called any time the block is placed into the world by the player

[xxKobalxx]

Where would i go as to placing this, im trying to add a single class where i can make a single cube (1/16 of a block) its basically a mini block class, am i looking in the right direction, im fairly new. I may have bitten off more then i can chew but i figured that would be a good way to learn.