The Frobozz Magic Passage Company was responsible for vast networks of corridors which were installed within the Great Underground Empire prior to its 883 GUE collapse. Their passages were made out of the same material as donut holes, and although many came off the production line only about a hundredth of a bloit long, once installed, were wide enough to walk through.

The following instructions accompanied each passage:

Hello, Builder!
   Your Magic Passage should last you for many useful years. To install, simply
INSTALL THE PASSAGE IN THE _____ WALL. Remember, your Magic Passage, once
installed, is not removable! Please contact your dealer with any questions or
   Another fine product of the Frobozz Magic Passage Company.

These non-removable passages could only be installed in a wall. A built-in safety feature prevented them from being installed in a vehicle. In certain enchanted places, some passages were repelled, as though two inconsistent types of magic were at work in the same place.

The Frobozz Magic Company had a strict code about the pristine quality of their passages. Unfit products, such as those that were slightly damaged or slightly irregular were marked for discarding (although nobody other than one of the bureaucratic Passage Inspectors would ever notice and most were perfectly usable).

The lower levels of the castle at Flatheadia once held a tremendous warehouse where passagesways and tunnels would be stored before being installed as part of the Great Underground Empire.

The reflection of one of these passages at Mirror Lake revealed its hidden magical properties, a feature which was invisible when gazed upon the passage with the naked eye: the edges dripping with unset glue.