nail down

British  

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

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nail down Idioms  

1. 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]

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Example Sentences

She gave them until early May to nail down a plan, otherwise they’d stick with the existing part.

From The Wall Street Journal • May 5, 2026

When Rupert’s children watched its too-close-for-comfort version of the chaos following Logan Roy’s sudden death, they leapt to nail down their family’s succession plan before it was too late.

From Salon • Mar. 14, 2026

EU-Swiss ties are currently governed by a patchwork of agreements, and the two have for years been striving to nail down a broader cooperation agreement.

From Barron's • Feb. 25, 2026

Clarke said he poured over recordings of the trial, listening to them first before he watched the videos, partly as a way to nail down the specificities of Alex’s accent and cadence.

From Los Angeles Times • Nov. 19, 2025

I had to tell her the good about Sophie, but it was hard to nail down.

From "Schooled" by Gordon Korman