Andrew Wasson of Creative Guitar Studio answers a viewers question…

The bass guitar’s neck has a logical mapping system based upon five scale positions. Each position will cover four complete diatonic modes. As well, each position also contains every diatonic 7th chord in key.
Each position covers 4 to 5 frets and will provide you with all of the notes you’ll need to create cool lines & phrases. Another interesting concept with these positions, is that by changing one note in a position, for example, while in the key of, “F,” you changed the, “E,” to an, “Eb,” you are able to change keys quickly, in this case from, “F to Bb,” without requiring any position shifting along the neck.