- Treenail
A treenail, trenail, or trunnel is a wood peg, or
dowel used to fasten pieces of wood together, especially intimber frame construction and woodenshipbuilding . It is an ancient technology. Coveredbridge s in the U.S. often use treenails as fasteners. Many such bridges are still in use.A method of making such a fastener was to cut a parallel peg of a softer wood, and then expand its outer end with a wedge of much harder wood driven into it.
Ancient shipbuilding used treenails to bind the boat together. They had the advantage of not giving rise to "nail-sickness" which is a term for decay accelerated and concentrated around metal fasteners. Increased water content also causes wood to expand, so that treenails gripped the planks tighter as they absorbed water
References
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