Throughout the years I've read a lot about the golden ratio from a design perspective. The Greeks noticed there was a common ratio in nature that was pleasing to the eye. This ratio is 1:1.618 (i.e. 1 to 1.618) and is referred to as the golden section. Today, you will find this golden section reflected in design of buildings, logos, products, artwork, etc.
I wanted to create a durable measuring gauge that would allow me to refer to this ratio when designing things that I build with wood, metal, software and other materials. The gauge in this instructable allows you to measure drawings or on screen items and keep the scale and proportion of elements in a design. And, because the golden section is about things that are visually appealing, I wanted the gauge to be visual appealing as well.
The gauge has 3 points, which always retains the ratio of 1 to 1.618, even as you expand and collapse the gauge. In the picture, the distance from the center and right point is always 1.618 times the distance of the left to center points.
WOOD magazine has great video regarding the golden section
with examples of the golden section in nature (your body), greek architecture and an example of how to use it to design furniture.
And you can read about it in Wikipedia
I was able to build this instructable for $1 and your results should be similar.
SIMPLIFICATION OPTION: If you don't want to hassle with cutting plastic on a bandsaw and torching it to get a nicer edge, there is an alternate approach (that I do not currently explain) that will reduce the effort and tools required for this instructable. I will create a followup instructable showing a simplified approach using wood.