A long wooden pin used in fastening the planks of a vessel to the timbers or to each other.

a wooden peg that is used to fasten timbers in shipbuilding; water causes the peg to swell and hold the timbers fast

a very dry wooden peg used to join timbers, esp

or trunnel; a wooden drift or dowel driven into the frame by which the hull strakes or planking may be secured to the ship's timbers. Treenails are also commonly used to secure wooden knees, and in scarphs etc.

Pronounced "trunnel" (rhymes with "tunnel"), a treenail, trenail, or trunnel is a wood peg, or dowel used to fasten two wood boards or beams together, especially in timber frame construction and wooden shipbuilding. It is an ancient technology. Covered bridges in the U.S. often use treenails as fasteners.