I think Brendan's description of Gua is the same one that I tried to come across. So I agreed with both him and Tainan.
All I am saying is there are 2 ways of Gua. It would seem that HK 7* favor what I would called Wei Gua (outer hanging) since that gua makes use of the outer edge of the arm (pinky side). The one described by Brendan is what I would call Nei Gua (inner hanging) since it makes use of the inner edge (thumb side) more. Now whether it is accompanied by a strike of the other hand or it becomes a strike in itself, it would be better to further discuss that. But basically, the action or principle of Gua would be IMHO laid out above already by different people.
BTW, I don't mean that Wei Gua equals karate's raising hard block. So relax.
Mantis108