fit together vs interlock

fit together

verb
  • To be able to be assembled in this way. 

  • To put the appropriate parts of (something) into a whole; to combine pieces that go together to create a finished object. 

interlock

verb
  • To fit or clasp together securely. 

  • To interlace. 

noun
  • A safety device that prevents activation in unsafe conditions. 

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