YOU SAID:
He's as dumb as a doornail
INTO JAPANESE
彼はドアネイルのように愚かだ
BACK INTO ENGLISH
He's as stupid as door nails.
INTO JAPANESE
彼はドアの釘のように愚かだ。
BACK INTO ENGLISH
He is as stupid as a nail on the door.
INTO JAPANESE
彼はドアの釘のように愚かです。
BACK INTO ENGLISH
He is as stupid as a nail on the door.
You've done this before, haven't you.