1. AN OPTICAL LINE INSCRIBING DRAFTING APPARATUS COMPRISING A SUPPORT FOR A LIGHT-SENSITIVE SURFACE, A LIGHT SOURCE DIRECTED TOWARD SAID SURFACE PHOTOGRAPHICALLY TO EFFECT EXPOSURE THEREOF, AND A SLIDE ASSEMBLY INTERPOSED BETWEEN SAID SOURCE AND SAID SURFACE AND INCLUDING AT LEAST ONE OPAQUE SLIDE HAVING A PLURALITY OF LIGHT PERMEABLE LINE-FORMING SLITS AT SPACED POSITIONS THEREON TO PRODUCE ILLUMINATED IMAGES OF DRAFTING LINES, SELECTIVE MEANS MOVABLE RELATIVE TO SAID SLIDE AND HAVING AN APERTURE THEREIN TO EXPOSE A SELECTED SLIT TO SAID LIGHT, AND MASKING