Playing within the box. The B.B. King Box is the pentatonic scale and includes the target notes 1, 4, 5 which also match the chord progression. It is convenient to play within the box without moving up and down the fret board with rhythm chord changes while playing a Riff because you can hit the target notes within the box and it still sounds good.
As an example, if you are playing in the key of D and the chord progression is D-A-G, you can continue to play the Riff in D during the chord change to A and G as long as you hit the target notes within the Box because you will be playing the D, A and G notes.
The Box is the comfort zone...kind of like the large screen TV and the dog and the dated dining room chandelier that you don't have to change out if you don't want to!
We were challenged to practice within the comfort zone; the Box. Also, start using swing notes and feel the music as you play. Do not play like your are speaking in monotone.