The target staff consists of two rods, which slide over each other. The two bars are held together by brass clamps. Extending the sliding can increase the length of the staff. The face of each rod is graduated in feet, tenths, and hundredths of a foot, while the back of the sliding rod is similarly graduated, but from top to bottom. The staff is provided with a moving target that has a vernier. With this vernier, one can read to 0.001 feet. The sliding rod carrying the target is bisected by the line of sight.
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