Spend enough time noodling on the fretboard and you start to notice some things. What follows is, in my opinion, one of the best approaches to understanding the neck as whole and that is - making comparisons.

You can teach yourself an awful lot about how the fretboard works just by recreating something you know in a different part of the neck either by sound or note value. You do-it-yourselfers can appreciate that. And the idea isn't limited only to scales, it applies to chords as well.

Because scales tend to involve more notes than chords and in fact are the source for chords, I'll use the mother of all scales, C major, to illustrate this concept. (And as a bonus, I'll throw in a little chord stuff.)

First, we'll start off with a very simple comparison.

Here's C major running straight up the 5th string illustrating the order of tones and semitones;

Now here's the same scale localized on three strings. Notice the visual representation of tones and semitones is different but it sounds the same;

* If it sounds the same, it must be the same! *

Have a look at the scale covering all six strings starting from the 6th string root. For the purpose of clarification, the image on the left was left unaltered, while the image on the right shows how the notes of a C major bar chord are contained or "caged" within the pattern;

(Note; Being able to envision a chord or scale, without your fingers on it, is a very cool thing. More on that at a later date.)

Now for comparison, let's see what C major looks like when it's built primarily behind the root fret;

And lastly, a form that works ahead of the root fret;

So which one is the right or correct form? Well, the answer is they all are. It's just a matter of preference. When I was first discovering this information for myself, I would see a scale form first printed one way, then another and then another! This confused the heck out of me until I realized it was simply a matter of the author's preference.  Which one you use is whichever one you like or does the job. Given enough time, you'll wind up using them all and these are just some of them. Now, how you use them is a different story...