Supression substractive Hybridization (SSH) - Some explanations (Nov/15/2005 )

Hello all,
does anyone have some experiences with SSH?
I want to identify some differentially expressed genes and i read a lot about SSH. it seems to be a great tool for that but always, if i try to understand the basics of that i get confused about driver, tester, target and so on. has anybody a link or an image which can explain that method in a few simple, maybe coloured sentences?
Thanks a lot

And another question : Why is my envelope locked?