crossbeam vs purlin

crossbeam

noun
  • A horizontal structural beam that runs perpendicular to the primary support beams; a girder. 

  • A beam laid across the bitts, to which the cable is fastened when riding at anchor. 

purlin

noun
  • A longitudinal structural member bridging two or more rafters of a roof. 

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