Treenail

from WordNet (r) 3.0 (2006)

treenail
    n 1: a wooden peg that is used to fasten timbers in
         shipbuilding; water causes the peg to swell and hold the
         timbers fast [syn: {treenail}, {trenail}, {trunnel}]

from The Collaborative International Dictionary of English v.0.48

Treenail \Tree"nail`\, n. [Tree + nail.] (Shipbuilding)
   A long wooden pin used in fastening the planks of a vessel to
   the timbers or to each other. [Written also {trenail}, and
   {trunnel}.]
   [1913 Webster]