Meaning of the word "(as) thick as two short planks" in English

What does "(as) thick as two short planks" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

(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

Idiom

1.

very stupid

Example:
He's (as) thick as two short planks, he never understands anything.
You'd have to be as thick as two short planks to believe that story.
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