Definition of "fid"

noun:
- A pointed tool without any sharp edges, used in weaving or knotwork to tighten and form up weaves or complex knots; used in sailing ships to open the strands of a rope before splicing. Compare marlinespike.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- A square bar of wood or iron, with a shoulder at one end, to support the weight of the topmast (on a ship).
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
verb:
- To support a topmast using a fid.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License