A riving knife is a piece of woodworking equipment that is used to prevent kickback when using a table saw. It is attached to the back of the saw blade and extends upwards so that it can contact the workpiece if it starts to kickback. Riving knives are an important safety feature on table saws and should be used whenever possible.
There are two main types of riving knives: fixed and removable. Fixed riving knives are attached to the back of the saw blade with screws or bolts, and they cannot be removed without tools. Removable riving knives can be quickly released from the saw blade for easy removal and replacement.
Riving knives must be properly aligned with the saw blade in order to work correctly. Most riving knives have adjustment screws that can be used to fine-tune the alignment. Once the riving knife is installed and aligned, it should not need to be adjusted again unless you change blades or make other major changes to your table saw setup.
If you're using a table saw without a riving knife, you're putting yourself at risk of serious injury from kickback. Always use a riving knife (or splitter) when making cuts on a table saw, and make sure it's properly installed and aligned before each use.