Correct

板上钉钉

/ bǎn shàng dīng dīng /
Strokes

Definition

that clinches it/that's final/no two ways about it

Example

Definition

be finalized; that clinches it; that's final

1
Zhège
这个
huà
计划
dàn
一旦
bǎnshàngdīngdīng
板上钉钉
  
,
jiù
néng
gēnggǎi
更改
le
  

Once finalized, the plan cannot be changed.

2
shuōhuà
说话
cónglái
从来
dōu
shì
bǎnshàngdīngdīng
板上钉钉
  
,
róng
不容
fǎn
反驳
  

There is always a definite finality in her tone, which defies any contradiction.

Related

板上钉钉