fine line

blur the line

To minimize or erode the distinction between two things.

bottom line

The summary or result; the most important information.

bottom of the line

The worst or lowest quality on the market, especially among a range of products.

bright line

A clear distinction in the context of a legal, moral, ethical, or analytical judgment.

chance'd be a fine thing

Synonym of no chance or fat chance, with a somewhat more cheerful attitude.

cross the line

To overstep a boundary, rule, or limit; to go too far or do something unacceptable.

down to a fine art

To a point of exceptional proficiency.

draw a line

To delimit a boundary or border.