to advance the board into the saw it will be understood by those skilled in the art that the bottom pinch rollers may instead be driven to capture the board or alternately that both the bottom and top pinch rollers may be driven the actual rip pattern a is shown to the operator by means of visible projected lines on the board at the projection area 140 and on the computer screen at console 200 though the operator would typically rely on the projected pattern various systems known in the woodworking industry may be used to project lines on the boards such as a shadowbox in which a bright light is projected against a series of strings to create line shadows or a laser system having one laser per line a preferred laser unit is lumber line lasers by john mccormick amp sons for each board the operator is able to choose from many alternate rip patterns for example if a different pattern b appears preferable to the operator perhaps to avoid ripping through a knot which would have resulted from using pattern a than he can choose that pattern and direct the system to align the board and present it to the saw accordingly as board 90 39 34 with pattern b in fig2 c the computer will at the same time post the calculated yield on the screen for that particular pattern the operator can by manipulating the board.