I make no bones about it; I use wedges 
Usually the first outside split is the wedge.
I did a small knife used for battoning thread a while ago. I'll see if I can find it.
I wouldn't normally use an opinel for this, but it was to hand, and I thought well, why not ? Give it a go.
Problem with the opinel is that the lock rings are really just finger saving devices and they're very bendable. I had my hand right over the joint on it tbh, just providing an extra stability.
The best results are obtained when the user remembers that the knife back should only be hit as hard as the other hand can hold the handle steady. Let it spring and you chance busting your knife.
Think of it like a froe, and like Yoda said, there is no try. Do or do not do.
One of these days this is going to come back and bite me, isn't it ?
I'm not advocating the use of the opinel or a stick tang for this technique simply because those are the most vulnerable *if* it goes wrong.
I do it, my friends do it, and we've yet to bust a knife. I suggest that practicing with something cheap might not be a bad idea for folks who don't get to use their knives very often. The only way to be confident using your knife, to learn it's limitations and abilities, is to use it.
cheers,
Toddy

Usually the first outside split is the wedge.
I did a small knife used for battoning thread a while ago. I'll see if I can find it.
I wouldn't normally use an opinel for this, but it was to hand, and I thought well, why not ? Give it a go.
Problem with the opinel is that the lock rings are really just finger saving devices and they're very bendable. I had my hand right over the joint on it tbh, just providing an extra stability.
The best results are obtained when the user remembers that the knife back should only be hit as hard as the other hand can hold the handle steady. Let it spring and you chance busting your knife.
Think of it like a froe, and like Yoda said, there is no try. Do or do not do.
One of these days this is going to come back and bite me, isn't it ?

I'm not advocating the use of the opinel or a stick tang for this technique simply because those are the most vulnerable *if* it goes wrong.
I do it, my friends do it, and we've yet to bust a knife. I suggest that practicing with something cheap might not be a bad idea for folks who don't get to use their knives very often. The only way to be confident using your knife, to learn it's limitations and abilities, is to use it.
cheers,
Toddy