The Green Brick Wall is the matching wall to the Green Brick, but it can not be crafted from the brick. It is only obtainable via removing it from a Green Brick dungeon with a hammer. Like all natural walls (such as Dirt Wall), it can only be removed from the edge. It allows Blue Armored Bones, Necromancer, Skeleton Commando and Paladin to spawn in the dungeon after Plantera is defeated.