Your basic component is a Door Frame. Each Door Frame type has its own max length, the lower tier frames are naturally shorter.
When you place a Door Frame, the face of the block you place it on determines which way the door goes (much like a piston in MC). If you place it while aiming at the side of a wall, it will extend from the side of the wall. If you place it while aiming at the floor, it will extend up, etc.
Once placed, aim at it and use X to interact. You will see yellow boxes extend from the frame. The boxes show how far the door goes: interact again to make it go 2. If it is a Heavy or Massive door, interact again and it will go 3, 4 ... etc. When you have interacted it to the length you want it to be, place DoorPanels or Glass where the yellow boxes were. As long as there are no empty spaces, any DoorPanel or Glass in the yellow boxes is now part of that door.
Add a switch to the DoorFrame.
Toggle the switch => Watch the door open. Toggle the switch again => Watch the door close.
For advanced users:
Conduit and DoorFrames carry signals, so you can run Conduit from your door to where you want the switch.
The Door can extend farther than you have door panels, this will let you "delay" it on close. The door will extend the empty spaces until finally extending the real panels. This allows you to sync up doors of multiple lengths. If you made a door that extended from above, for example, you could set a few frames side by side, each extending down. If you made them all 5 long, but only put 4 door panels every other row (leaving a blank at the bottom of that row), when you close the door you'll notice it maintains its toothed edge.
If someone in the community that has a good knack for using these doors wants to post a quick tutorial video to youtube, that could be pretty handy.
And here's a great tutorial made by none other than dstruxon!

http://www.youtube.com/watch?v=g2jyG3Al ... e=youtu.be