Are there trap doors in Terraria?

Trap Doors are furniture items. They are essentially full-block horizontal Doors. Trap Doors can be opened by right-clicking, causing them to expand into a 2x2 block. They are valid for use in housing. Trap Doors open upward if the character opening it is below the Trap Door's level, and downward if above. read more

Trap Doors open upward if the character opening it is below the Trap Door's level, and downward if above. The reference point for character altitude seems to be the character's center, not the feet: the character's feet can be about one half tile below the bottom of a closed Trap Door (standing on a stair), and the door will still open downward. read more

As of Terraria 1.3 (June 30th) there are trapdoors. They are two blocks wide and one block tall, they are exactly like doors but sideways and smaller. Right click to interact. read more

Doors can be placed in any space so long as it is exactly three blocks high, with ceiling and floor blocks. Friendly NPCs will open and close doors during the day as they wander about. Enemies that follow the Fighter AI can open doors, with a few exceptions. read more