Or the wedge method is when you don't want to kill your only knife (which means break, dull, etc)

You could also use Pitman's method of stabbing it and prying it apart. I wouldn't try this unless I had a DMCG. You could incorporate Pit's method and the wedge method if the log is too thick for the knife and the knife is just too thin. Overall many bushcraft knives (meaning to insanely thick and beastly), should be able to handle itself after being batonied tip first into the wood.

But the wedge method can seriously save your skin... and your knife.