There is usually more to selection of where to baton in the wood than how to actually baton which is as simple as hit the knife with a stick and drive it through the wood. You go by the same basic principles of dealing with knots as you do when splitting wood in general.
With folding knives you can release the lock and baton them through softer woods. As the wood gets harder to split you will need to engage the lock to allow the blade to actually be driven through. The impacts are however very severe at this point.
Unless the folder is really robust this stands a great chance of breaking the lock. What you can do is just split the wood enough to drive in a wedge and use that to finish. The wedge can just be another piece of wood or even a rock.
There is an arguement proposed by some, that the knife should never go off horizontal when batoning as this raises the stress on the knife (it doesn't), and that you should never press down with the off hand as this also makes it much harder on the knife (it does and a *lot*).
However simply because it makes it harder doesn't mean the knife should be unable to do it. A tempered steel blade should not fracture from impacts with a stick when in a piece of wood and there are lots of makers that won't impose such limitations on their knives.
-Cliff
