Abstract: A reference plane producing method and system wherein a substantially collimated beam of electromagnetic radiation, for example, a laser beam, is reflected to simultaneously disperse the beam in different directions to form a thin plane of such radiation which can be used, for example, as a construction reference line. In a preferred embodiment a primary cone having its apex projecting towards the incident beam and its optical axis coaxial with the incident beam is used to reflect the beam of light. Various embodiments of a basic apparatus having integral or separate collimating and leveling devices are described. The preferred source of radiant energy is a laser, most preferably a second-mode laser having a donut or annular shaped beam and is projected against an axially aligned conical reflecting surface. The conical surface can be a female cone formed by axially drilling into a transparent transmission tube, such as the emission end of a fiber-optic transmission system.