On a level with the eye of the observer, as of a picture hung in on a wall.
(idiomatic) At risk, as in a contest or enterprise.
The survival of the company is on the line with this project.
Currently calling on the telephone.
I have John on the line for you.
(sports) On one of the lines marked on a playing field or court; (by extension) within bounds.
The ball was on the line but the umpire ruled it out.
What I admire most are people who put themselves directly on the line. Donald Trump
So when the blue smoke of brittle leaves was in the air and the wind blew the wet laundry stiff on the line I decided to come back home. F. Scott Fitzgerald
Entrepreneurs are risk takers, willing to roll the dice with their money or reputation on the line in support of an idea or enterprise. They willingly assume responsibility for the success or failure of a venture and are answerable for all its facets. Victor Kiam
The police officer who puts their life on the line with no superpowers, no X-Ray vision, no super-strength, no ability to fly, and above all no invulnerability to bullets, reveals far greater virtue than Superman - who is only a mere superhero. Eliezer Yudkowsky
I think if you are writing an instrumental you are dealing with more of an aesthetic in a sense but a lyric is more of a putting yourself on the line and a much more expensive exercise. Leo Kottke
People who put themselves on the line and sacrifice their own safety for the greater good and for others, and anyone in any profession whose concern is the welfare for other people instead of the individual, are inspiring and important. Chris Hemsworth