The Design of a Marking Rule

By The Metric Maven


I’ve discussed the design of rulers a few times before. I’ve always been amazed at the number of options which have been used to define their divisions, and label their values. The website BoingBoing introduced me to another option for ruler design-–stenciled holes. The Incra website has a  millimeter metric-only ruler with stenciled holes that allow a person to mark distances with great precision. I could not help but purchase a 300 mm version to see how well it works. To the left is the label which boasts that this rule is a new 300 mm long metric, albeit 300 MM on the label.

click to enlarge

The first thing one notices is that the numerical labels for the holes and slots bounce up and down. I suspect this was done with the intention that separating the numbers spatially, would make it easier to distinguish them. In my view, it tends to be a bit of a distraction, but this type of separation has been used on other rulers and seems workable. This is a minor concern as Incra offers millimeter-only rules of this type in the US, which is of great utility when other options are limited.

The rules are flexible enough to conform to many objects and allow for accurate marking.They are also essentially stencils, and without pressure, do not return to a flat planar state under their own weight when placed on a flat surface. They are not really designed for use as an everyday ruler, but are for woodworking projects and other designs which might need a conforming rule with precision measure.

Below is a close-up of the left end of the rule:

click to enlarge

Incra has a lot of marking options on these rules. They have openings that will just accommodate a 0.5 mm Pentel mechanical pencil lead. One must extend the pencil lead far enough out to protrude through the hole or slot as the outer lead guide is too large to fit. The zero marking spot on the left hand side of the rule for both the line and single dot markings is cut in half to maintain the best accuracy possible. In the case of the dots at the center they start with half and are stepped in case you want even more accuracy and option.

A video shows how certain versions of their rulers allow you to mark dots and lines with ease, but they tout their inch-length versions and only casually mention that metric versions are available. If a person misguidedly insists they must have both a US inch and millimeter scale, the best version in my view is the 10″ decimal/mm marking ruler. The top scale is millimeters which is a clue that metric is the preferred scale for measure. Below is the inch scale which is marked in tenths of an inch with 1/20″ openings between. Recall that a millimeter is about 1/25″ and is the most precise measurement increment on the scale.

Related essays:

The Design of Everyday Rulers

Stickin’ it to Yardsticks

The American “Metric Ruler”

America’s Fractional Mind

If you liked this essay and wish to support the work of The Metric Maven, please visit his Patreon Page and contribute. Also purchase his books about the metric system:

The first book is titled: Our Crumbling Invisible Infrastructure. It is a succinct set of essays  that explain why the absence of the metric system in the US is detrimental to our personal heath and our economy. These essays are separately available for free on my website,  but the book has them all in one place in print. The book may be purchased from Amazon here.

The second book is titled The Dimensions of the Cosmos. It takes the metric prefixes from yotta to Yocto and uses each metric prefix to describe a metric world. The book has a considerable number of color images to compliment the prose. It has been receiving good reviews. I think would be a great reference for US science teachers. It has a considerable number of scientific factoids and anecdotes that I believe would be of considerable educational use. It is available from Amazon here.

The third book is called Death By A Thousand Cuts, A Secret History of the Metric System in The United States. This monograph explains how we have been unable to legally deal with weights and measures in the United States from George Washington, to our current day. This book is also available on Amazon here.

5 thoughts on “The Design of a Marking Rule

  1. For the longest time, I’ve had a couple of steel tape measures that have inches down one side and centimeters down the other.

    About a month ago, one of them broke – and the other one has a crack in the metal tape, so it’s going to die very soon.

    So I head off to Home Depot to buy a new tape measure – and to my horror, every single one of them has only inch markers! I checked Lowes, and then an increasing number of other stores – and it seems to be that every single tape measure on sale in the USA is now inches-only.

    This is a mighty leap BACKWARDS. I’m quite horrified. I’m going to the UK for a vacation in a few days – and I’ll have at least a few inch/metric tape measures in my bag on the return trip!

    • True in brick and mortar stores. More choice online. You will find a wide selection of metric/inch and metric-only tapes online (Amazon has a good choice but so do others).

      When b&m stores refuse to carry what I’m looking for, I don’t feel the slightest bit bad for them and their current troubles.

  2. The marking on that ruler looks like a weaning tool for the inch user.

Comments are closed.