The Graveyard Keeper 2 smithy, in four points
Two buildings share the name, and only one of them is the station you researched. Every figure below comes from community material, tagged with its source and date rather than stated as a game fact.
スミスと呼ばれる建物は2つ
The Factory Smithy is a crafting station a zombie works, inside the underground Factory below your base. The Town Smithy is a shop with a trader, on a Workshop Courtyard plot in town, behind the Artisans I research. They share a name and nothing else.
ヤードのデスクには出ない
Because it is a Factory station rather than a Yard one, the Smithy only appears at the building desk inside the Factory. If the research is bought and the Yard desk still does not list it, you have not reached the Factory yet — that is the whole of the problem the guide page is answering.
Smithy I is 75 red and 20 blue, past Iron Smithing
The community wiki tree prices the node at 75 red and 20 blue points and the guide repeats it; the build adds 6 Reinforced Plank, 4 Bronze Detail and 4 Bronze Gear, and the frame is finished with a Hammer at Building mastery 4.
燃料ではなく石炭で動き、ゾンビが作業する
The smelting recipes take Coal rather than the Fuel a furnace burns, materials arrive on Conveyor Belts, and those belts are driven by zombies on a Zombie Carousel. You cannot work a Factory station yourself.
