Do not transmit on 121.5 unless in emergency or to send a message concerning the safety or regularity of flight.
Capt P, in general I'd agree but I don't think it's too much of a misuse, as ejectx3 and green granite suggest, to use it to call someone over to 123.45 or pass an ATC freq (although that would come under 'send a message concerning the safety or regularity of flight')
ps: Don't stand any nonsense from that young Humphries
