Some guitarists can solo happily anywhere on the neck of their guitar: Knowing the scales is only half of it.
The other half is being able to play the various inversions of the scale.
When most of us sit down and learn a scale, we learn it in the root position. Usually, with the root on the sixth string, but sometimes we’ll learn the fifth string root pattern of the scale as well.
But the scales can really be maxed out by starting on another scale step. Using the Pentatonic Blues Scale in A, for example, the guitarist could start on the second scale step. In this example, the first finger plays “C” by fretting at the 8th fret as a starting point.
And the scale can also be played starting on any other note in the scale as explained in this video.
Knowing the various inversions of the scale allows the guitarist to switch keys without having to change positions on the neck: Happily.