A blind dado is a hidden joint used to make bookcases. On the sides of the bookcase, dadoes are cut most of the way through the board. The shelf has a small notch that fits over the uncut part of the board. Use a 3/4" stacked dado head raised 1/4" above the table. With the table saw unplugged for safety, turn the dado stack until finding the spot where the dado stops cutting. Use a combination square to mark that spot on the fence. Later, use this mark as a reference point for starting the dado cut. Plug the saw back in and turn it on. Make a plunge cut into a board using the mark on the fence as a starting point.