Special walls are floor objects. There are two main types of Special Walls: Moveable and Fake.
These are walls that will be converted to flooring, the secret passages that open up, eg clicking the button opens the wall (moveable wall) to reveal a path.
Deactivating the moveable wall removes them. Activating a moveable wall creates a wall.
These look like normal walls, illusionary walls, but can be entered, by the party, monsters, objects and spells.