What good's a fireproof safe if the only guy who could enter the combination has retired?

How to say “What good's a fireproof safe if the only guy who could enter the combination has retired?” in Japanese

In Japanese

ダイヤルを合(あ)わせる番号(ばんごう)を知(し)ってたのが一人(ひとり)だけで、その人(ひと)が退職(たいしょく)しちゃったら、耐火(たいか)の金庫(きんこ)でも意味(いみ)ないよね。

Daiyaru o awaseru bangō o shitteta no ga hitori dake de, sono hito ga taishoku shichattara, taika no kinko demo imi nai yo ne.

What good's a fireproof safe if the only guy who could enter the combination has retired? in other languages