What is a method of leveling a line or surface by sighting along the tops of two or more straight edges, or a range of properly spaced poles. See 3d Bone, v. t called?

boning — A method of leveling a line or surface by sighting along the tops of two or more straight edges, or a range of properly spaced poles. See 3d Bone, v. t. (Webster's 1913.)

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