Crossword clue: a long wooden pin used in fastening the planks of a vessel to the timbers or to each other.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
a wooden peg that is used to fasten timbers in shipbuilding; water causes the peg to swell and hold the timbers fast