hammer-headed vs not the sharpest crayon in the box

hammer-headed

adj

  • Having a head in the shape of a hammer 

  • stupid, ignorant 

not the sharpest crayon in the box

noun

  • Synonym of not the sharpest knife in the drawer 

How often have the words hammer-headed and not the sharpest crayon in the box occurred in a corpus of books? (source: Google Ngram Viewer )