I forgot:

http://www.hardwaresource.com/newsdetail.asp?ID=12

which describes it fairly well...

Keith Boeheim wrote:

I am taking on a project that is bigger than I have done before. An 8
foot entertainment wall unit in 2', 4', 2' sections. I have built the
carcases but I am stuck on the doors. How do I predict the size I need
for the face frame cup hinges? Is there a difference in overlay when the
door is closed and when it is open and if so which overlay size to you
buy for?. I have visited Rockler's web site but the info is still
sketchy to me.

Thanks for any help

kb