set square vs straightedge

set square

noun
  • A flat triangular piece of plastic or other material, having corners of precise angles, used in technical drawing 

  • A right angle tool used to determine if two surfaces join at a 90-degree angle, composed of two arms, usually made from metal. 

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 set square and straightedge occurred in a corpus of books? (source: Google Ngram Viewer )