LEVELING-STAVES, instruments used in levelling, serving to carry the marks to be observed, and at the same time to measure the heights of those marks from the ground. They usually consist of two mahogany staves ten feet long, in two parts, that slide upon one another to about 5½ feet, for the more portable carriage. They are divided into 1000 equal parts, and numbered at every tenth division by 10, 20, 30, &c. to 1000; and on one side the feet and inches are also sometimes marked.
A vane A slides up and down upon each set of these staves, which by brass springs will stand at any part. These vanes are about 10 inches long and 4 inches broad; the breadth is first divided into three equal parts, the two extremes painted white, the middle space divided again into three equal parts, which are less; the middle one of them is also painted white, and the two other parts black; and thus they are suited to all the common distances. These vanes have each
a brass wire across a small square hole in the centre, which serves to point out the height correctly, by coinciding with the horizontal wire of the telescope of the level.