The phrase "a permanent line" is correct and usable in written English.
It can be used to refer to a line that is intended to last indefinitely or is not meant to be changed or removed.
Example: "The artist decided to draw a permanent line on the canvas to define the boundaries of her work."
Alternatives: "an enduring line" or "a lasting line".
All the while, however, the Leeps were hunting for a permanent line of business, something to sustain their 20-year-old family firm.
The two sides did agree to open a permanent line of dialogue on defense issues and to set up a team to continue discussing weapons sales.
Egg Shop opened on the Lower East Side in August 2014, with a permanent line out the door of enthusiastic — and particular — regulars.
Nasa's fond farewell to the aged shuttle fleet draws a permanent line under 30 years of missions that defined modern space flight, but the US space agency cannot afford to dwell on its past achievements.
But a growing number of Obama's supporters on the left fear the concession will act as a permanent line in the sand, making it impossible to resist future pressure to reduce spending on welfare.
So people being given a mobile number thinking they now have a permanent line in to someone else's mobile device may well get a nasty shock when they find the number wasn't so permanent after all.
Supporters still intend to ask the city for a permanent line-item subsidy of $1 million a year.
Among the proposals were tax cuts, a permanent line-item veto, and a constitutional amendment requiring a balanced budget.
Among the proposals were tax cuts, a permanent line-item veto, measures to reduce crime and provide middle-class tax relief, and constitutional amendments requiring term limits and a balanced budget.
In early tunnels, timber was used for the initial or temporary support, followed by a permanent lining of brick or stone masonry.
Townsend recruited a permanent line-up for the second album: Jed Simon on guitar, Byron Stroud on bass, and Gene Hoglan on drums.
