A chalk line, or chalk box, is a tool that is used for laying out straight lines on flat surfaces, or marking sheet material and lumber stock for cutting. Using this tool will be more precise than pencil lines, especially marking over longer measurements. Chalk lines usually have 50 to 100 feet of thin line wound around a reel in a small case containing chalk powder.
To mark a line, you gently tap the case to coat the line with chalk, then pull out the line taut, and snap it with your finger and thumb pinching it. Most modern chalk lines do double duty as plumb bobs. The plumb bob is simply a pointed weight on the end of a string line used to find vertical points via gravity.
Making a Clean Chalk Line Mark
Position the hook at the end of the chalk line string over the edge of your work surface, for example a floor joist or wall stud. If there is no edge available, hook it over a temporary nail in your surface.
Stretch the line down to the other end of where you want your line to go, and hold the chalk box against the work surface.
Pull the line away from this surface, holding it between thumb and forefinger, and let go of it so the line snaps back, leaving a nice clean line mark of chalk.
You’ve just made a perfectly straight line for driving a series of nails along, laying rows of tiles down on, or starting a roofing tile course.
You can now buy laser chalkline devices which automate this process. These are mostly useful for larger area jobs or volume work where manual laying out would be too time consuming, but they are fun gadgets to have even so.
For example, this Dewalt DW082K Self-Leveling Laser Plumb Bob kit projects two beams: one is projected plumb up, the other plumb down. The tool needs to be just placed on the floor and the on/off switch pressed. The advantages? The line is unaffected by wind, it settles in seconds, and leaves both the operator hands free. Similar units are available which function horizontally.