Chalk Line

A chalk line, also called a chalk box, is a tool for marking long, straight lines on a relatively flat surface, over distances well beyond what a person could manage by hand or with a straightedge. It works by stretching a taut string that has been coated with a loose powdered dye, usually chalk, across the surface to be marked, then plucking or snapping the string sharply so it strikes the surface and transfers the chalk along a straight line; the tool can mark across irregular or gapped surfaces, such as an unfinished stud wall. Chalk lines are ancient, used in ancient Egypt and mentioned in Homer's Iliad, and have been used continuously by builders in many cultures since. The tool remains a basic part of carpentry today, especially for laying out unfinished timber, and is often sold together with a plumb bob for marking vertical lines as well as horizontal ones.