roofing vs sprocket

roofing

noun
  • Material used on the outside of a roof, such as shingles. 

  • The process of constructing a roof or roofs. 

  • A way of travel which consists in clambering over the roofs of skyscrapers. 

sprocket

noun
  • A flared extension at the base of a sloped roof. 

  • A toothed wheel that enmeshes with a chain or other perforated band. 

  • The tooth of such a wheel. 

  • A placeholder name for an unnamed, unspecified, or hypothetical manufactured good or product. 

How often have the words roofing and sprocket occurred in a corpus of books? (source: Google Ngram Viewer )