Double doors treated as one door

[extant1]

When two doors are placed next to each other with handles pointing towards the center the door opening key will open both doors together.

[SatsukiShizuka]

Would love to contribute to this by proposing that a 1-wide double door be added for various tiers, to allow for narrow house designs. http://indulgy.com/post/Tg3qyqe451/chinese-door