This is a piston door that has a delay before closing. The difference between this and other doors is that there is a very short delay before opening, but a long delay after opening with the use of an rs nor latch and repeaters. I'm probably also going to make a pressure plate version in which the door closes after you step on them. Even though this is built with a piston door, it can still be used with a normal door, though I think you would have to flip the redstone for one door.

This would probably be used for a puzzle or adventure map.

Additional Notes

The delay can be changed by changing the repeaters shown in the video.
Can be used to trap people =D