This is a term from the past but one way of fastening old planks on wooden boats still. In the past they were the only fasteners used.
In this application I think its as much an issue of pluging the old plank holes?
The issue is that as the boats planks become old they can soften, fasteners such as nails or screws can
pull right into the plank, they can and will cause nail rot over time.
Ancient shipbuilding used treenails to bind the boat together. They had the advantage of not giving rise to "nail-sickness", a term for decay accelerated and concentrated around metal fasteners. Increased water content causes wood to expand, so that treenails gripped the planks tighter as they absorbed water. Similar wooden trenail fastenings were used as alternatives to metal spikes to secure rail-support "chairs" to wooden sleepers in early Victorian times.
In this application I think its as much an issue of pluging the old plank holes?
The issue is that as the boats planks become old they can soften, fasteners such as nails or screws can
pull right into the plank, they can and will cause nail rot over time.
Click on the picture for a larger image.
The pegs have been fitted with what looks like phenolic glue, they then hold the plank to the new frames inside the hull. I suspect this set of tree nails is as much a way of pegging old nail holes and a secondary set of nails and coach bolts with doublers on the plank ends be fitted?
Read more on the subject below.
http://en.wikipedia.org/wiki/Treenail
Roy