Snip of very complete description of tree nails from Nick:

> Trenails, or pins,  are most easily made from very dry stock,
> ripped in long lengths,  and planed from the square to a
> slightly oversized octagon shape.

> The idea is to get the corners to bite into the wood of the
> timbers, and then have them swell as they wick moisture from
> the less-dry timbers.

> The stock for these cannot be too dry.

Reading this makes me wonder if the combination of very dry
pegs and wetter surrounding timber will be susceptible to the
same effects as the mortise and tenon joints in Windsor chairs.

In his early stages, Mike Dunbar used to recommend that the
tenon material be very dry so that it would swell to lock the
joint together.  But later, he said that was a mistake, because
he realized that, as it swelled, the super-dry tenon would
compress the wood fibers around the mortise which would lead
to a looser joint during subsequent wet/dry cycles where the
tenon and mortise might shrink away from each other.  I
believe this is his current thinking anyway.

- Bill