Meaning: hard to get through to or to effect change (example)


Rewrite 1: cement headed
Rewrite 2: steel haired
Rewrite 3: mind with the welcome mat turned upside down
Rewrite 4: brain with the access panel welded shut
Rewrite 5: opinions guarded better than the vault at Fort Knox


Comment: There is a sense of this idiom which is quite literal, but mostly it means stubborn; thus, the rewrites about close-mindedness. 


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Speaking of stubborn opinions
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