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

Instead, nail down the parts that are boring.

From Barron's • Feb. 7, 2026

"There's a term called 'RuneScapiness' which is a little bit hard to nail down," game designer Molly Mason told the BBC.

From BBC • Jan. 5, 2026

He ran a nail down the heavy cartridge backing and stripped it away to reveal...

From "Artemis Fowl" by Eoin Colfer