So ....... there are no rules, right?

Like Bonnie, I have to understand it first, now I can just get on with it. I guess a really good use might be to enable me to play some of the really difficult chords that my old fingers won't otherwise reach. I take your point Bill (\sables) about using it as an excuse not to learn the chords but some of them really boggle my fingers!

Thanks all for great explanations.

Cheers, Terry