Doors are pretty common elements in most buildings. Creating a door in Inform is like having another room between the two rooms that a door connects. Here is a simple example of how to create a door.
A Basic Door was created with Inform and has IFID 210C7325-5825-4B66-ABF3-A01CA10EFBFA. To play a work like this one, you need an interpreter program: many are available, among them Zoom
for Mac OS X and for Unix; Windows Frotz or Windows Glulxe for Windows.