hatstand vs thick as a plank

hatstand

adj
  • Crazy, insane. 

noun
  • A device used to store hats upon, consisting of a vertical pole with a sturdy base to prevent toppling, and an array of pegs to hold the hats. 

thick as a plank

adj
  • Very stupid. 

How often have the words hatstand and thick as a plank occurred in a corpus of books? (source: Google Ngram Viewer )