Hi Bob,

Don made some important distinctions. Are you asking about pegs, (trunnels) or wedges for drawn joinery. Don's description is spot on, and we would have to know which method you are talking about to fully answer any questions.

To add to Don's description, most trunnels are a minimum of ~2/5 longer than the material thickness they are meant to pass through. You will find variances in this, of cores, but that is a mean average as observed in both North American house/barn wrighting and Asian timber wrighting modalities; sometimes that may even be ~1/2. So, for example, if you have a 200 mm (~8") post your trunnel will be 280 mm to 400 mm long. The extra length gets the tapered end outside the joint and also allows you to trim the striking end of the trunnel, should it start to "mushroom," or "split apart," before you have driven it all the way through.

Regards, jay