The noExit object can be used to block an exit that would otherwise be set as a reciprocal exit by Room.preinitThing(). This can be used to prevent this extension from creating symmetrical exits in cases where you don't want them. E.g. if north from the smallCave leads to largeCave, but south from largeCave doesn't lead anywhere (because the notional passage between the caves curves round, say), then you can set largeCave.south to noExit to prevent this extension from setting it to smallCave.

The noExit object is thus a TravelConnector that simulates the effect of a nil exit in situations where a nil value might get overwritten by this extension. [SYMCOMM EXTENSION]

noExit :   TravelConnector