Abstract: A compact, low-cost, hand-held builder's tool for use in defining reference lines perpendicular and parallel to a specified surface. The tool comprises a housing that is generally small enough to fit conveniently in the user's hand and that includes a battery-powered laser for projecting a visible laser beam through an exit window in the housing over an extended range. An on-board alignment mechanism is provided within the housing for adjusting and setting the alignment of the laser beam in fixed disposition for establishing an accurate reference line. The housing has two generally parallel broad faces joined by a plurality of connecting faces extending substantially perpendicular to the broad faces. One of the broad faces and two of the perpendicular connecting faces taken together define three reference planes that are mutually perpendicular to one another within a margin sufficiently small that the tool has an accuracy suitable for use over an extended range of at least about 20 ft (about 6.1 m).

Abstract: An electrically responsive level of the type used for determining inclination with respect to a gravity field is described. The instrument relies for its operation on a bubble-within-a-vial type of inclination sensor. The vial is generally rectangular in cross-section, and its dimensions and the size of the bubble therewithin are selected to assure that the instrument can be used reliably in the field without false readings and the like. The specific leveling instrument described is of the so-called carpenter's type and is usable not only to provide a visual and/or audio indication of a level condition, but also to measure or establish any inclination between the horizontal and vertical.