# Shop Tips & Tricks #7: Measuring Things - The Two-Foot Folding Rule

 Blog entry by GnarlyErik posted 12-09-2012 09:08 PM 6326 reads 3 times favorited 6 comments
 « Part 6: Measuring Things - Rulers Versus Tapes Part 7 of Shop Tips & Tricks series Part 8: Laying out irregular areas and surfaces »

“More Than You Ever Needed to Know about Two-Foot folding rules”

Let me say up front that I am most familiar with the six-foot folding rule. That said, I will share with you some things I have learned about two-foot rules. Most common are those with four joints, known as ‘Two-foot, Four-Fold Rules’, and you can do many things with them.These were typically carried in a workman’s shirt pocket, or in the side pocket on the right leg of most overalls of the time. There were also two-foot, six-fold rules made to make them even smaller to carry, but those never were as popular. Historically, most carpenters and woodworkers used the two-foot rule until the late ‘forties and into the ‘fifties when the six-foot folding rule gained favor. But, many old-timers from the ‘forties and ‘fifties and before favored them and continued to use them until they retired or died off. I’d imagine you will still find some in use today, but increasingly rarely. I own one, but don’t use it much, mostly because I grew more familiar with the six-footer.

Working ends of American versus English measurements

Here are a couple things you can do with a two-footer that are hard or impossible to do with anything else:

First, you can lay out angles up to 90 degrees with a two-foot rule, without using math for those who find numbers difficult. Expert workmen had a few angles memorized, say 15, 20 and 30 degrees. Other angles could often be derived from those. You simply mark a straight line of a specific distance to represent the angle desired. You then open up the legs of the rule and placed one leg on each end of the line. The angle you need is made by the legs. For example, if you need 15 degrees, the measurement is 3-1/8”, for 20 degrees it is 4-7/64”, for 30 degrees it is 6-7/32” and so on. There actually used to be tables published with a complete list of measurements for all angles to 90 degrees and these might be tacked to the shop wall. (A far more convenient way used by most boat shops was a ‘Bevel Board’ with all angles needed scribed on it, and one simply needed to use a adjustable sliding tee bevel to pull off the required angle. See below)

And, then there is the “3, 4, 5 rule” for right angles which most layout folks know. Simply put, a line 3 increments long has an arc of 4 increments swung from one end, and 5 increments from the other, and where the arcs intersect is the end of the leg forming a right angle with the “3” end. Conversely, you can start at the 4 increment leg and swing a 3 increment arc and get the same result. The sweet thing about this, is that any multiple works so long as the proportions remain the same. If you are unfamiliar with why this works, google the ‘Pythagorean Theorem’ online.

Another thing two-foot rules can be used for is to layout octagons for turning square stock into octagons, and then rounds. That is described in the blog entry “Centerlines – Finding, Marking and Using them, Part Two” http://lumberjocks.com/GnarlyErik/blog/33328

In fact, it is written two-foot rules once came with two extra symbols on them labeled “E” and “M”, many years ago just for laying out octagons, but I do not know just how those worked. Perhaps they were at the 7” and 17” marks.

I am getting way off subject here, but there are several other kinds of ‘Two-Foot Rules’ which are interesting:

In football, the Two-Foot Rule; “Two feet must come down within bounds to have possession of a passed ball”;

In bee-keeping, the Less Than Two-Feet or More Than Two-Mile Rule; “When moving a bee hive, you must move it less than two feet, or more than two miles in order for the returning bees to re-locate it”;

With domesticated rabbits, the Two-Foot Rule; “If you don’t want it eaten, it must be more than two feet off the ground.”

The Open-Space Technology Two-Foot Rule for meetings, symposiums and conferences: “If at any time during our time together you find yourself in any situation where you are neither learning nor contributing, use your two feet, go someplace else.”

And, getting way far out there now, during the 1918 Influenza epidemic, Pasadena, CA passed an ordnance called the ‘Two Foot Rule’. It was only permissible to hold open air meetings in public places, so long as all attendees kept a distance of two feet apart! Apparently this rule was enforced and people were cited for non-compliance. There was a run on two-foot rules wherever they were sold! You just can’t make this kind of stuff up!

For anyone who is interested in owning a two-foot rule, new ones can still be bought made by the Robert Larson Co. You can also find them on eBay in all manner of condition. And, if you want a really nice one made the old way, and your checking account can stand it, you can find antiques in remarkably good conditions sometimes. Here are a few sources:

Liberty Tools, Maine – http://www.libertytoolco.com/
Rose Antique Tools – http://www.shop.roseantiquetools.net/
Tool exchange – Australia. – http://toolexchange.com.au/ (this one is in Australia, but will ship to the US and has a good reputation)

-- Candy is dandy and rum sure is fun, but wood working is the best high for me!