Life was different back when measurements were homey approximations. The basic units were from the human body, a handy tool you always had with you: a foot was the average man’s foot, an ell was his forearm from elbow to middle fingertip. Other units derived from work: a furlong was the length of furrow a horse team could plow without a rest, an acre the area an ox team could plow in a day.

None were exact until commerce took them beyond the homestead. At some point it mattered that a carat, based on the weight of a carob seed, be codified, and that an inch be more precise than three barleycorns in a row.

Now we all have tape measures and rulers, but on my own small domain I find it handy to know that my four knuckles are three inches across and my thumb knuckle almost one, for rough calculations. A step in the old days was about a yard, and my husband, Eliot, is quite accurate at pacing out yards with his particular stride.

Sometimes the implements we commonly use become measuring tools in addition to their specified uses. Fifty- or 100-foot-long hoses give a quick picture, as do the eight-foot sections that make up our fence. In fact, when you look at our farm and gardens, their layout and management show an interplay between the size of our bodies and the way we use favorite tools.

All our beds are 30 inches wide, measured with a tape and based partly on our four-row seeder, which makes 12 correctly spaced carrot rows to the bed, with three lengthwise passes. That bed width is also what the shortest person in the farm can step over easily without treading on plants and the maximum reach she can make to weed the center without straining her back.

This system also ties in with the 29-inch-wide rake we use to form our beds and then mark them for transplanting. The rake, available from Johnny’s Selected Seeds (, has bent teeth over which we put markers made of red plastic tubing. These markers make visible lines in the soil as you draw the rake lengthwise down the bed, spaced according to how wide the planting rows should be. After marking the rows, you reset the markers according to how far apart each plant should go in the row, then draw the rake across the bed to make a grid. A plant goes at every intersection of the lines.

For each crop, there is a number code based on how many bare teeth there are between red markers. So if we tell someone to “plant the lettuce at 6-7” it means that there should be six bare teeth between markers when you draw the lines for the rows and seven bare teeth when you draw the lines crosswise for the individual plants. It’s not only quick, it makes the beds look perfect.

So we can chuckle about an old measurement like the rod (20 feet), derived from the length of an ox goad. But whoever first thought to use it was no dummy.

Damrosch is a freelance writer and the author of “The Garden Primer.”