steel square vs straightedge

steel square

noun
  • A tool used to measure out right angles. 

straightedge

noun
  • A flat, rectangular tool used to draw, cut or check the straightness of straight lines. 

adj
  • Living one's life opposing or eschewing the use of substances such as alcohol, tobacco, and drugs. 

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