Often referred to as the "Four-Way Door", this is a combination of the Star Trek Door and the Split Door. It's very decorative, despite it's simplicity in construction.
Construct a Star Trek Door, but tag the door sector [0,26]
instead of [0,9]
.
In 3D mode, give the floor and ceiling of the triangles a nice texture. Then raise the floor and lower the ceiling of the triangles so they meet in the middle. The Star Trek Door texture will be covered by an ugly brown brick texture. Replace the ugly brown brick texture with a nice door texture.
Now your door will work in the game! It should open like this:
If you trigger it twice really fast, sometimes the floor and ceiling will close when the side doors open, and vice versa! This makes for an interesting glitch. Note: The door sound will still play twice, just like the Star Trek Door.