There was a fine line between the good guys and the bad guys.

好人和坏人之间只有一线之差。

《柯林斯英汉双解大词典》

He was walking a fine line between being funny and being rude.

他想滑稽而不粗鲁，难以把握分寸。

《牛津词典》

There is a fine line between showing interest in what someone is doing and interfering in it.

关心别人正在做的事情和进行干预之间存在着细微的差别。

《牛津词典》

But he points out that President Obama must walk a fine line: encouraging democratic change without threatening regime change.

VOA: standard.2010.05.19

Milton's treading an extraordinarily fine line between the tremendous beauty of this image, on the one hand, and its potential impiety or just grotesquery on the other.

弥尔顿踩到了一条极其微妙的分界线上,这幅景象一方面极具美感，另一方面却可能是对上帝不恭甚至荒诞的。

耶鲁公开课 - 弥尔顿课程节选

President Obama is walking a fine line in his 2011 budget.

VOA: standard.2010.02.01

Pinault walks a fine line between being a student of artists and their patron.

WSJ: Collecting Art With Fran?ois Pinault

Mr. Marer says he skates a fine line between enjoying exercise while shunning overt competition.

WSJ: Hockey Heats Up in Tiny Village With Israel's Only Big Rink

But there is a fine line between form and function in the case of custom bikes.

FORBES: Why You Need a Custom Road Bike