The hand level, like all surveying levels, is an instrument that combines a level vial and a sighting device. It is generally used for rough leveling work. In a cross-sectional work, for example, terrain irregularities may cause elevations to go beyond the instrument range from a setup. A hand level is useful for extending approximate elevations off the control survey line beyond the limits of the instruments. Figure 11-28, view A, shows a LOCKE HAND LEVEL; view B shows an ABNEY HAND LEVEL.

For greater stability, both hand levels may be rested against a tree, rod, range pole, or on top of a staff. A horizontal line, called an index line, is provided in the sight tube as a reference line. The level vial is mounted atop a slot in the sight tube in which a reflector is set at a 45 angle. This permits the observer, while sighting through the tube, to see the landscape or object, the position of the bubble in the vial, and the index line at the same time.

The distances over which a hand level is sighted are comparatively short; therefore, no magnification is provided for the sighting.

The Abney hand level is more specialized than the  Locke type. It has a clinometer for measuring the vertical angle and the percent of grade. The clinometer has a reversible graduated arc assembly mounted on one side. The lower side of the arc is graduated in degrees, and the upper side, in percent of slope. The level vial is attached to the axis of rotation at the index arm. When the index arm is set at zero, the clinometer is used like a plain hand level. The bubble is centered by moving the arc and not the sighting tube as is the case in the plain hand level. Thus, the difference between the line of sight and the level bubble axis can be read in degrees or percent of slope from the position of the index arm of the arc. The 45 reflector and the sighting principle with its view of the landscape, bubble, and index line are the same as in the plain hand level.

Figure 11-28.-Types of hand levels.