Definition of "nail down" []

• To attach with nails (verb)
• To make something (e.g. a decision or plan) firm or certain (verb)

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• "So they forged an alliance with all the trust of a Palestinian-Israeli handshake, because in the end, both sides knew that they needed to gather and nail down the evidence fast – before Crimstein mucked up the waters."
• "Morris teamed with Thomas Fitzsimmons to nail down the senator he needed when the two joined George Read, a moderate Delaware Federalist, for a long Sunday ride outside the city and persuaded him to switch his vote."
• "On their 147th and last pitch of the night, Madson got Teixeira to chase a one ball-two strike changeup in the dirt to nail down the 8-6 win."