Barring with the thumb?

[Tony_Iommi]

I heard on well...heh. Marc Seal's page, via one of the lessons, an interesting snippet about Jake E. Lee (From Ozzy's band..for the Bark at the Moon and The Ultimate Sin albums) That he barred some chords with his THUMB?! what? how's this work? is it even effective?

[The Fury]

I've never heard of Jake E. Lee so I dont exactly know what I'm on about.
But I know jimmy Hendrix used to use his thumb for some chords, example of a movable add9 chord with the root note on the 6th string (I think)

fingers used-T means thumb, x-do not play
el--4
Bl--1
Gl--2
Dl--3
Al--x
El--T

Frets used for an Aadd9
el--7
Bl--5
Gl--6
Dl--7
Al--x
El--5

Alternativly, if it was in drop D tuning, you could use your thumb to barre strings 6, 5 and 4 and use your other fingers to embellish the chord (added notes etc..). I've tried both of these and they are not too difficult.