After some 'development iterations' I show my version of an aspect ratio calculator slide rule. As this 
enhanced version has undergone significant changes and additions compared to the basic version once provided 
by 'Workshop Warlock' on mailleartisans.org , I will provide a new manual now, that shows and explains these 
changes - for the basic explanations please follow the instructions of my forerunner, as they are not only 
sufficient, but excellent. But I try to give them here as well. 

Download, print (and feel free to save a local copy) of the PDF file provided here. You need Adobe Acrobat 
Reader(TM), Foxit Reader or another software that can handle PDF files to be installed on your PC for this. 
Alternatively I can provide a .GIF file for you per mail - just ask for it. 

After printing the slide rule page on approx. 160gsm (~8 mils thick) strong paper or maybe light cardboard 
(letter or A4 format preferred, just check 'fit to page' to get the largest possible result), you should cut 
out, separate parts, fold and glue the item together, as noted on the left margin of that page. After gluing 
the body part, you may cut notches at its left and right ends to be able to push the slider easier out of its 
centered "parking" position (as shown above) - or simply cut the body a bit shorter, if you like to do so. 
Then stick the slider into the body, so its scales are visible through the slots (I note that, because some 
people seem being too d... to imagine this - but I guess these would be unable to use this tool at all, so I 
don't worry too much about them). The slider should be relatively easy movable, but without any wobbling, as 
that would destroy the principally high precision of this tool. So you might be forced to make corrections or 
even a repetition of the print and cut, until it works out well. Just be as precise as you can achieve, and 
do NOT use less effort as when making a fine piece of maille - using ruler and knife for cutting may be a 
good idea. 

The basic principle of that AR calculator, and explaining the principles of logarithmic scaling are beyond 
the goals of this article - I propose the interested ones to look up Wikipedia or a good maths book for "slide 
rule" and/or "logarithm". But the shortest possible explanation I can give is, that the use of logarithms is 
to enable someone to MULTIPLY numbers by ADDING their logarithms looked up at a precalculated table, and 
looking up the number accompanied to the addition's result at the same table (divisions are made by subtracting 
logarithms). And that principle can be embedded in a device made from two rulers, where numbers are shown in a 
logarithmic scaled grid instead of a linear one, so direct multiplications can be made by adding lengths in 
that grid. 

Complicated explanation aside - the mode of use is really simple: Shift the slider in a manner, that the wire 
diameter on the body scale is aligned with the used ring inner diameter - and the AR can be read directly at 
the lowest tongue scale at the point aligned with the triangular 'Aspect Ratio' mark. Naturally you can do this 
calculation in different directions, e.g. for determining a needed ring ID by given wished AR and existing wire 
diameter - set the AR on the lower scale, and simply read the corresponding ring IDs for given wire diameters. 
And last but not least needed wire diameters for given ring size and AR can be determined the same way. For a 
more 'graphic' description on the tool's use you maybe look up the article of the original AR calculator on 
mailleartisans.org. 

Just align the given known data, and read the to be determined ones. Easy, isn't it?