Iron Door

The Iron door Door is a Placeable object, similar to other furniture, with the added benefit of preventing the passage of enemy NPCs. It can be placed in any space so long as it is exactly three blocks high, with a ceiling and a floor.

Iron doors are functionally identical to Wooden Doors. Town NPCs will open and close doors as they wander about. Players can do the same by right-clicking on them. Enemy NPCs will not open doors except for Skeletons, Undead Miners, Goblins and Angry Bones. Zombies and Possessed Armors can also open doors during a Blood Moon, and Goblin Peons can break down doors, as if they were destroyed by a player.

Doors can be opened and closed through Wires. If you put wire on one of doors closed state squares, then wiring will toggle closed/open states upon activation, but if you put wires on the side squares, where door opens, then wiring will only close door.

Tips

 * Doors open to the left or right based on which direction you face, rather than the direction you are coming from. For example, if a player stands to the left of a door and faces left, the door will open toward the player - to the left. If the player doesn't move and then turns to the right and opens the door, it will now open to the right.
 * Putting furniture (even the second door) on one side of the door prevents it from being opened in that direction. This is useful to keep houses safe from Zombies during the Blood Moon or most Goblins, as they'll always attempt to open the doors inward, while still allowing NPCs to go in and out as they please.
 * Doors can also hold back water.
 * Doors will break automatically if exposed to lava while open, but will hold back lava like water while closed.
 * Digging a 2x2 block deep hole in front of a door will prevent goblins and zombies from attacking it.