nail something down
https://gyazo.com/0fc7692d206cb48421643bf718f05193
nail something down
1. fasten something securely with nails.
〈物〉をくぎで留める
2. identify something precisely:
〈原因など〉を明らかにする, 突き止める
e.g. something seems unexpected—I can't nail it down, but it makes me uneasy.
3. secure something, especially an agreement:
｟主に米｠ A〈協定など〉を確定する, 最終決定する.
e.g. the company has finally nailed down the agreement with its distributors.
#phrasal_verb