How to Make a Chalk Line
by Damien Andrews
Snapping a chalk line is a great way to make a straight line over a long distance. In fact, before the introduction of laser devices which shoot straight lines, it was the only convenient and effective way of making a straight line over a long distance. And with laser devices still costing triple digit money, and not being suited to all tasks, the low-tech chalk line still sees a lot of duty with carpenters, masons, and do-it-yourselfers.
Chalk lines are used for many things, but I am confident in saying that the chalk line is most often used when marking 4' x 8' sheets of materials for cutting. Again, I am confident in saying chalk lines are snapped on plywood and drywall more often than on any other materials. Since do-it-yourselfers work more often with plywood than with drywall, we'll be discussing snapping chalk lines on 4' x 8' sheets of plywood.
To snap a good chalk line, you need to acquire a good chalk reel or chalk line reel. Same animal, different names. You'll also want to get some good chalk – the most popular colors are blue and red, and in fact even finding another color is difficult. Purchasing both products should cost you less than $10.00. NOTE: if your selected chalk line reel already has chalk in it, be sure to purchase the same color chalk for refilling it.
Our 4' x 8' sheet of ½" plywood is sitting nicely on our saw horses. We want to use a circular saw to cut the 4' edge, cutting off pieces that are 16" wide for shelving. So we must snap a chalk line that is 4' long. First, measure the 16" in from the 4' x 8' sheet of plywood's 4' edge – twice: once along each long side of the plywood. (See Diagram A)
Vigorously shake your chalk line reel to ensure that the chalk line is fully dusted with marking chalk. Now, have someone take the end of the chalk line out of the chalk line reel and pull it out far enough to do the job – about 5'. There will be an attaching eye or loop of metal or tough plastic on the end of the chalk line that is pulled out of the chalk line reel (we'll talk about that later). Don't pull the line out directly over your work – to avoid excess chalk dust on your board.
Have your helper hold their end of the line such that it hangs down over the edge of the plywood, with the line covering the 16" mark as it passes over it. Now you pull your end over the edge of the board and apply a tiny bit of pulling pressure. (See Diagram C) Check your chalk line to ensure it is over both marks precisely. If it's not, relax a little and make the final adjustments. When both marks are covered with the line, pull it very tight. Double check that your 16" cut marks are covered and then reach out towards the center of the taught chalk line, pinch it, lift it straight upwards until the tension is very noticeable – then release it. Have your helper release their end, lift the chalk line reel up and away from the plywood and reel the chalk line in. You should now have a perfectly straight line for a perfect 16" cut. (See Diagram B)
Okay, so you don't have a helper – that's what the chalk line reel has that eye on the line for. Tap in a short nail to hold the eye in place where you want the far end of the chalk line held. For best results, attach the nail under the sheet of plywood. (See Diagram D) If you try to nail on the top of the plywood, you'll have great difficulty lining up your chalk line on the first mark. You can hang the chalk line reel over the other edge carefully to apply a slight tension while you align the marks to the line itself. Be sure to double check your mark after you snap the chalk line. Remember the carpenter's #1 rule: measure twice – cut once!!!
Excess chalk line dust can easily be brushed away or vacuumed up. Avoid using any moisture for cleaning it off – that can get messy, and even permanently stain the wood. It is also difficult to cover with paint. If you work with chalk lines extensively, or in areas with poor ventilation, the use of an appropriate dust mask is recommended.