The phrase "a safe line" is correct and usable in written English.
It can be used in contexts where you are referring to a line of communication or a boundary that is secure or protected.
Example: "In our negotiations, we need to establish a safe line to ensure that sensitive information is not compromised."
Alternatives: "a secure line" or "a protected line".
D. F. Manley: A safe line won't let anybody bel/t up - idly conceived plan must go.
Perceptive readers will have spotted a safe line of play for ten tricks: win the opening lead with the spade king, not the ace, and play trumps.
The 65-page indictment, which was accompanied by a guilty plea from one lobbyist who said she had participated in the scheme, includes wiretap transcripts in which targets fretted about whether they were on a "safe line" or if "friends are listening".
Expenditures included renting of the "patient briefcase", establishment of a safe line for data transmission and use of hospital staff.
Leaving that heated argument aside, I can propose a safer line of thinking: that of the passing of time.
In the majority of paediatric patients and in 30% of adult patients, the choice of a P-PICC was related to the need for a reliable, safe line for power injection of contrast medium, considering that in many patients (particularly in children) peripheral veins for insertion of a short cannula of appropriate calibre for contrast injection were not available.
It did not take Mercedes long to come out with a safe party line.
So it's a safe applause line, for anybody except a funky postmodern anti-anti-colonialist like Dinesh D'Souza; but I doubt he was in the audience.
"Herpes is a safe punch line in an era of comedy where making fun of someone's race, gender, sexual orientation, disability, and class is increasingly considered politically incorrect," she wrote.
The future must not belong to those who bully women – it must be shaped by girls who go to school, and those who stand for a world where our daughters can live their dreams just like our sons.It's not always a safe applause line to bring up girls' educational rights as part of a discussion of religious tolerance and civil rights in the Muslim world.
