ridgepole vs sprocket

ridgepole

noun
  • A beam along the ridge of a roof to which the rafters are attached. 

  • A horizontal pole that supports the roof of a ridge tent 

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 ridgepole and sprocket occurred in a corpus of books? (source: Google Ngram Viewer )