Abstract: A manually manipulatable gyro-stabilized indicating instrument which may be used by pipefitters, carpenters, builders, land and road graders and the like for solving a construction problem involving determining the orientation in space of an unknown geometrical plane with reference to a known geometrical plane, or using a known or unknown geometrical plane as a reference and either establishing in space a geometrical plane having a predetermined orientation with reference to the known or unknown geometrical plane. The instrument has at least one straight planar surface and a gyroscope or gyroscopes operatively connected to the straight planar surface and having motive means for driving the gyroscope or gyroscopes to a continuous stabilized condition relative to the straight planar surface in any fixed position and location assumed by the straight planar surface at the time the gyroscope becomes gyroscopes become stabilized.