For use upon machinery in a wood shop or any industrial facility where it is desired to operate upon an object's unmarked centerline, such as with a powered saw table, drill press or any other apparatus required for the task: The sine and cosine of a triangle—are used to assure that as a certain component is moved a given distance, a guide fence is moved transversely just a fraction of that distance—preferably one-half—away from or toward the task performing instrument—a saw blade, drill bit or other operable tool. Thus, if the distance moved by the component equals the width of the piece to be worked upon, where the trigonometric sine is such that the guide fence is moved half that distance, given certain further adjustment, the task performing instrument is caused to operate precisely upon the piece's centerline, represented by one-half its width.