A support for a laser beam generator in a carpenter's level is positioned on the level so that the laser beam generated will lie in the plane of a flat reference surface of the level. A battery or other power supply is housed in the carpenter's level together with circuitry to connect the power supply...http://www.google.fr/patents/US5604987?utm_source=gb-gplus-shareBrevet US5604987 - Laser level, accessories and method of use
