noun
solemn promise
General sense of a firm, unbreakable promise. Often used in modern contexts to emphasize the seriousness of a vow.
彼は金打の約束を守った。
He kept his solemn promise.
noun, noun or participle which takes 'suru', intransitive verb
promise sealed by striking metal objects together
Historical practice where samurai struck swords or women struck mirrors to seal a vow. Now a literary or explanatory term.
武士たちは刀を打ち合わせて金打した。
The samurai struck their swords together to seal the promise.