This command allows you to lock clients into specific channel masks. Using this method you can use an NNTP like naming structure to do:
Adding those two masks means that clients will only be able to join any channels that are under #news. and #entertainment. like #news.lobby or #entertainment.shows o #entertainment.event
ADD - Add a client channel locks.
DEL - Delete a client channel locks.
LIST - List all specified channel locks.
/as help client set chanlock <channel>
This command set is nice to add a structure to your channel naming conventions.