Abstract: To determine and block the orientation of a lens located in only one location by both its refractive characteristics and lay-out properties preparatory for edge grinding relative to a template pattern, two scenes: a refractive scene and a lay-out scene are produced by light passed through such lens. One or more emissions of light are directed by one or more of the following: (1) one or more beam splitters and (2) one or more mirrors. In some embodiments, the two scenes can be observed separately, in others superimposed by optical or electronic devices. Simultaneous production of both scenes visually demonstrates Prentice's Law, P=hd. When a shadow receiver is present to receive shadows of non-marked multifocal segments in the lay-out scene, the width of the emission of light used to produce the refractive scene is defined by one or more apertures of such shadow receivers.