They are instanly acecssible from anywhere on the fretboard, yet many players overlook them in solos.
A simple pattern would be:
Tap the 12th fret, pull-off to the 8th fret, then the 5th, then to the open string.
|-(t)12-p-8-p-5-0-----(t)12-p-7-p-4-p-0--