In carpentry–unlike other disciplines, such as the study of language or business training, for example–filling out one’s toolbox is not just a metaphor.

Since enrolling in construction school in September, I have acquired a motley selection of tools, including a Ryobi palm sander, Husky utility knife, and my beloved DeWalt jigsaw. At the top of my wishlist are a circular saw, hammer drill, and impact. But this weekend I acquired one of my favorite gadgets: a chalk line.

Used since ancient Egypt, chalk lines are handy for marking straight lines on surfaces that are too long for a level or other typical straight edge. For example, need to mark a horizontal line to start siding the exterior of a house? Chalk line. Need to rip a long board with crooked edges? Chalk line.

A chalk line is kind of like a tape measure, but instead of a windup ruler, you have a spool of twine saturated with powdery chalk. Unroll the string where you want to make a straight line, pull it taut, then use thumb and forefinger to pluck the string, making it snap against the surface and imprint it with the powdered chalk.

I love this tool for its elegant commonsense. I also like it because it requires a certain dexterity of thumb and forefinger that, for a fleeting instant, makes even the most hulking carpenter look like he just might extend his pinky finger while sipping from a china teacup.

I bought my chalk line at an estate sale, where I found it in almost pristine condition in a well-ordered workshop stocked with tiny engraving tools and drill bits of every possible diameter. I like to think the chalk-dusted string ties me to a long line of people who trusted themselves to make and fix things.

I was so proud of my new gadget that I showed it off to my teenage son when I got home. At first, he regarded my demonstration with as much interest as if I were showing him how to employ a spoon. I worry that he believes a smart phone is the only tool worth owning. But when the string snapped, leaving a perfect line along the length of the kitchen counter, he conceded, “OK, yeah, that is pretty cool.”