(as) thick as two short planks

US /əz θɪk əz tuː ʃɔrt plæŋks/
UK /əz θɪk əz tuː ʃɔrt plæŋks/
"(as) thick as two short planks" picture
1.

非常に頭が悪い, とんでもなく愚か

very stupid

:
He's (as) thick as two short planks, he never understands anything.
彼は非常に頭が悪い、何も理解できない。
You'd have to be as thick as two short planks to believe that story.
その話を信じるなんて、よっぽど頭が悪いに違いない。