Two function rooms, Empress and Media Room, have hard keys, and the rest are cardkeys.  Since it is the only thing on the 16th floor, Charles View can also be secured by locking off the elevators from that floor and securing the (hardkey) stairwell doors.  Any room can be "rekeyed" for $50.  This does not make the room strictly client access only, but it does guarantee that no previous customer has access, and limits hotel staff access somewhat.
 
Two function rooms, Empress and Media Room, have hard keys, and the rest are cardkeys.  Since it is the only thing on the 16th floor, Charles View can also be secured by locking off the elevators from that floor and securing the (hardkey) stairwell doors.  Any room can be "rekeyed" for $50.  This does not make the room strictly client access only, but it does guarantee that no previous customer has access, and limits hotel staff access somewhat.