slide rule vs straightedge

slide rule

noun
  • An analog calculator consisting of three interlocking strips marked with logarithmic scales, such that multiplication, division etc. can be performed by the equivalent of addition and subtraction. 

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