A riving knife is a safety feature on a table saw. It is very similar to a splitter on a table saw, and as a result is often confused as one. The difference is that a riving knife is attached under the table so it goes up, down, and side to side with the blade. Additionally it does not need to be removed for doing non through cuts. It prevents kickback back not allowing lumber to ride on the back of the blade.
On an additional note while these have been standard in Europe for some time all new table saws in the United States will have these as of 2009.
http://www.raygirling.com/ryobi/ryobi.htm
On an additional note while these have been standard in Europe for some time all new table saws in the United States will have these as of 2009.
http://www.raygirling.com/ryobi/ryobi.htm