Doors are blocks that can be used as barriers to be opened or closed. In Update 34 variants of the vanilla door were added for each wood added by the mod. Most of the textures were made by the Polish Noble. They can be found throughout the Structures of Middle-earth.
These new doors could not be added earlier in the mod's development due to a lack of vanilla support for modded doors (meaning that if doors were added, NPCs would not be able to open them). As a result they could only be added after Public Beta 32 when the mod first included a coremod, allowing the NPC AI to be modified. The new doors themselves were then added in Update 34.
In addition to the normal wooden doors, there are two special doors. One of them is the vanilla iron door, which can only be opened by Redstone power sources, and is made using six iron ingots instead of wooden planks. The other is the Dwarven Door, which is made of (and resembles) stone and cannot be opened by NPCs.
As stated earlier, most of the mod's humanoid NPCs are now capable of opening doors. While they can't see players or other NPCs through closed doors, they will open them if they come across one. Therefore, if you wish to keep NPCs out of an area, you might want to opt for a Gate or fence gate instead.
Note: the wood names in this gallery are links to the relevant tree and can be followed for more information.