nail down

verb

1. to fasten down with or as if with nails

2. informal,  to extort a definite promise or consent from

   I nailed him down on the deadline

3. informal,  to settle in a definite way

   they nailed down the agreement

Idioms and Phrases

Establish conclusively, as in The reporter nailed down the story by checking all the facts. This metaphoric expression alludes to fixing or fastening something down with nails. [c. 1600]

Example Sentences

County and plaintiff lawyers nailed down the $4-billion figure on Oct.

From Los Angeles Times

They know nothing more about either man than they did in April – Pope missed his chance to nail down the spot and Bethell barely played.

From BBC

But that short-term testing alone won’t be enough to nail down a more refined estimate of the retrofit cost, the county CEO’s office said.

From Los Angeles Times

If the project cannot nail down funding sources, Choudri said it faces considerable challenge.

From Los Angeles Times

He has been deployed as a centre-back, central midfielder and a winger in his time at Pittodrie - versatility which managers love but which often makes it difficult to nail down a particular spot.

From BBC