くぎ
kugio sasu

Godan Verb (su)
Idiomatic Expression

1. to give a warning; to remind (a person) of; to drive in a nail — literal

実際 じっさいはそんなことあるわけないが、釘 くぎ すにはちょうどよさそうだ。
jissaiwa sonna koto aruwakenaiga kugio sasuniwa chōdo yosasōda.
There's no way something like that would really happen, but it seemed just right to drive the point home.
Other forms: