Chalk line

A chalk line or chalk box is a tool for marking long, straight lines on relatively flat surfaces, much further than is practical by hand or with a straightedge. They may be used to lay out straight lines between two points, or vertical lines by using the weight of the line reel as a plumb line.

It is an important tool in carpentry, and the working of timber in a rough and unplaned state, as it does not require the timber to have a straight or squared edge formed onto it beforehand.