Hey guys, I understand how a table saw's riving knife makes cutting safer by holding the cut open behind the blade, preventing the wood from pivoting, contacting the side of the blade and kicking back. However, I don't understand why it has two positions—above the blade, for through cuts: ...and even with the top of the blade, for non-through cuts (e.g. kerfing): It's obvious the knife can't be higher than the blade during non-through cuts. But the rest of the time, what's the advantage of having it higher than the blade? Is there a reason to keep putting it back up there?