Rusty hammer

The equips the the  slot and is used when constructing blueprints and during several other select operations. The can be found in the graveyard trunk at the start of the game or can be purchased from the Blacksmith. It is currently believed that the hammer tool progression is bugged as Rusty hammers are a high level craft at the anvil II and iron hammers require steel and have the steel hammer sprite in-game.

Efficiency represents how much progress toward an operation each swing of the Hammer provides. The provides the base 100% efficiency.

Energy usage represents how much energy each operation consumes. The requires  per swing.

Studying at the Study table will give you.