The Smithe Gate is a near impenetrable steel gate that guards the Forges of Smithestone. It is named ironically after House Smithe. The overseer of the gate' is given the title Lord Defender of Steel and Silver.
The Smithe Gate began it's construction a decade before Lord Orroman Harrigon died. With the castle rebuilt, Lord Orromus began the construction of Smithestone's forges. His descendants would replace the wooden gate with an array of different metals over time, from Steel, to Silver, and finally Valyrian Steel after Aegon Targaryen's conquest. The lord of Smithestone is named the Shield of Steel and Silver for this very reason. The Gate is manned constantly, not to allow outsiders to see what House Harrigon is building inside the forges.
Following the Stormmoot, Lord Rickard has the Smithe Gate opened, releasing many of the secret weapons House Harrigon has built. He brings them with him to Storms End under the guard of his most trusted bannermen.