“板上釘釘”，漢語成語，本義指在石板上釘上鐵釘（nail the slate with nails），比喻事情已經(jīng)決定，不能改變或事情已經(jīng)成了事實(shí)。與英文慣用語“cast in stone”意思相近，表示“Completely set, unchangeable; not subject to any amendment or alteration”。

例句：

他只是提出這個觀點(diǎn)供討論，事情還沒板上釘釘。
He is merely throwing the idea forward for discussion. It is not cast in stone.

雖然我很想?yún)⒓樱俏业萌コ霾?。而且我知道，日期已?jīng)不能再改，是板上釘釘?shù)氖铝恕?br>While I really want to attend the party, I'll be on a business trip. And I understand the date of the ceremony can't be changed. It's cast in stone.

Editor: Jade