A chalk line, chalk reel or chalk box is a simple hand tool consisting of a box with a reel of string inside it. The box is filled with chalk powder and the string, once coated with it is reeled out and used to mark straight lines. On the end of the string is a metal hook which can be attached to an object. Once the string is positioned it can be \u201cplucked\u201d at the center and the tension forces it to snap back down leaving a chalk line on the surface, sometimes known as \u201csnapping the line\u201d. Generally used for marking long, straight lines on relatively flat surfaces much farther than is practical by hand or with a straightedge.<\/p>\n\n\t