@open

The @open command is used to open a new exit from this
room to a different room ID. The destination must be a
room. Every exit must have a destination, although it is 
possible to @lock an exit so that it never succeeds. Many 
synonyms for the exit's name can be provided to accommodate 
reasonable guesses on the player's part. The destination
can be changed later using the @link command.

Usage:

@open n;north;out = #322