Green’s Dictionary of Slang

on the line phr.

[gambling use]

1. honest, straightforward, in the open.

[UK]Ally Sloper’s Half Holiday 3 May 2/1: As an ‘on the line’ man said to me—‘Mima, dea— I mean, Miss Sloper’.
[Aus]Bulletin (Sydney) 13 Sept. 35/2: Oh, I suppose they’d have to be a woman – if only to keep the doctor on the line.
[US]D. Runyon Runyon à la Carte 88: You will tell her to get it on the line at once and save herself trouble.
[US]E. De Roo Go, Man, Go! 105: Pa wanted it on the line. He was keeping Paul awake to have it out.
[UK]T. Wilkinson Down and Out 131: If what you’re saying is really on the line and straight, then there’s no reason why they can’t review your case.

2. of money, either put at stake or, e.g. in the case of a drug deal, advanced as a loan.

[UK]Sporting Times 9 June 1/5: I’m the P.C. with landscapes on the line, I am. You surely don’t expect a R’yal Academician to ruin his hands by mixin’ up in street scraps, do ye?
[US]Hostetter & Beesley It’s a Racket! 233: on the line—Immediately; ready and waiting; e.g. ‘He put down $150 on the line.’ NOTE—A term borrowed from aviation and used on landing fields to indicate a plane that is ready to take off.
[US]D. Runyon ‘Gentlemen, the King!’ in Runyon on Broadway (1954) 174: He [...] will lay twenty-five G’s on the line.
[US]F.S. Fitzgerald ‘A Man in the Way’ in Pat Hobby Stories (1967) 37: I hate to give an idea without money on the line.
[US]H. Simmons Corner Boy 44: Wasn’t many guys Monk would let have junk without cash on the line.
[US]J. Ellroy Brown’s Requiem 12: I [...] told him to meet me at my place in an hour and to bring coffee—there was work on the line.
[US]B. Hamper Rivethead (1992) 152: The problem was Eddie simply got the yips whenever money was on the line.

3. (US) prepared, in the offing.

[US]P. Crump Burn, Killer, Burn! 48: Everytime I get a lay on the line, something messes it up.

4. under interrogation.

[UK]G.F. Newman You Flash Bastard 124: Even an important QC, a judge almost, cringed when on the line.

5. (Aus.) under police observation.

[UK]J. Morton Lowspeak.

6. (US prison) for sale.

[US]Other Side of the Wall: Prisoner’s Dict. July [Internet] On the Line: For sale (L.A. County Jail).

In phrases

put one’s ass on the line (v.) (also put one’s balls on the line) [ass n. (4)/balls n. (3)]

(US) to put oneself into a position of responsibility, to take risks; to face punishment.

[US]J. Wambaugh Secrets of Harry Bright (1986) 269: Maybe Harry put his ass on the line once or twice for Coy.
[UK]B. Geldof Is That It? 135: Jesus, if they found out, my balls would be on the line.
[UK]J. Hawes Dead Long Enough 9: If a TV Exec is going to put himself and his balls on the line for anything, it will be for something that combines proven ratings and alleged heavyweight learning.
[UK]M. Collins Keepers of Truth 140: I’m putting my ass on the line for you, Bill. Don’t let me down.
[UK]Indep. 16 May 30/6: Whose arse is it on the line if the whole thing goes tits up?
put someone on the line (v.)

to place someone in a difficult or challenging position.

[UK] in R. Graef Living Dangerously 183: Luke put me on the line within two hours of my arrival.
[UK]K. Richards Life 321: The idea of putting the whole tour on the line because I couldn’t make it was too much, even for me.