Watch the E Form: Trill Exercise online guitar lesson by Dave Celentano from CAGED Commander

The entire trill exercise sits nicely in the 'E form' scale pattern except the 12th fret/A and D strings, which are relocated from the 7th fret/D and G strings. Another way to understand the 'out of the pattern' notes is to think of them as 'borrowed' from the next pattern (in this case the 'D form', which is the next pattern in the CAGED systym).