...that after memorizing one 2-octave fingering, you will be able to play any major (=ionian) /dorian/ phrygian/ lydian/ mixolydian/ minor (=aeolian) and locrian scale anywhere on your neck. That's 7*12=84 scales total!!!

Here's what you do:

chances are, you're already familiar with this "standard" major scale fingering, which starts on your 2nd finger (and, btw, ends on your 4th finger):


















 

HOWEVER... that only let's you play your C-major scale in 3 different places on your neck. You can dramatically increase your "coverage" (actually to 100%) by also memorizing this fingering, starting on your 4th finger (and, btw, ending on your 2nd finger!! also note the little "shift" between your 5th and 6th scale degree - this is very important!!):






















And here's the punch line: now that you know that the fingering starting on your 2nd finger ends on your 4th finger, and the one starting on your 4th finger ends on your 2nd finger, it is a "no brainer" to combine those two to create one 2-octave fingering.
Played across 5 strings, if you start on your 2nd finger, after covering one octave you can continue using your 4th finger version:


















 

(continued!)