(as) thick as two short planks
US /əz θɪk əz tuː ʃɔrt plæŋks/
UK /əz θɪk əz tuː ʃɔrt plæŋks/

1.
más tonto que un zapato, muy estúpido
very stupid
:
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He's (as) thick as two short planks, he never understands anything.
Es más tonto que un zapato, nunca entiende nada.
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You'd have to be as thick as two short planks to believe that story.
Tendrías que ser más tonto que un zapato para creer esa historia.