What does it mean when a CW operator sends “KN” at the end of a transmission?

In Morse code, prosigns are combinations of letters sent together to control the flow of the conversation. The prosign "K" by itself means "over" or "go ahead," acting as an open invitation for any station to reply. When an operator sends "KN" at the end of a transmission, it restricts that invitation. It means they are listening only for the specific station (or stations) they are already in contact with or just called. Other stations must stand by and not transmit. Distractors such as "Closing station now" apply to different prosigns entirely. "SK" is used to signify the end of a contact, and "CL" means the station is going off the air.