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Phrase(s): use your head for more than a hatrack [and] use your head for more than something to keep your ears apart
Rur. to think. • How are we going to solve this problem? Come on, use your head for more than a hatrack. • Instead of whining about it, why don’t you use your head for more than something to keep your ears apart?
McGrawhill's American Idioms And Phrasal Verbs