The Engineer's Guild allows the recruitment of engineers for gold. Freshly recruited troops gather at the guild's entrance, unless an assembly point is set. A rally point can be placed to a custom location per troop from the building panel, which can be reset to the guild itself.
Engineers in Stronghold Legends can repair walls and use the oil smelter. Standalone engineers will automatically take stone blocks from the stockpile and use them to fully restore a damaged wall segment when they find one.
When an oil smelter is built, the game automatically recruits engineers to man it and assigns them to oil duty, up to three. Engineers with oil can be freely commanded around and they return to the smelter for fresh supply after pouring it.
While most siege engines from the siege camp are seen operated by engineers, they automatically come with the engine and do not cost extra funds.