Watch the All Boxed Up online guitar lesson by Andrew Ford from Blues Bass Survival Guide
We start with the some box shaped lines. The first 12 bars here are shorter triplets, a little more staccato. Then there is the triplet figure that leads us to the 4 chord. Same box shape in D then another triplet leads us back to the 1 chord. There is a walk up(connecting the dots) to the 5 chord, more box shapes then a turnaround figure in bar 12. The next 12 bars are longer triplet figures used in a walking line. Almost every chord is connected using a chromatic passing tone.