For this to work properly you have to plan your sites navigation so all directories or indexes can be reached with a single jump. This also means that you can't be totally reliant on images for navigation. Personally I believe you should have text links to all indexes at the bottom of every page. The best way to show you how to do this is a quick demonstration. I'm going to use a computer site to demonstrate this because we should all be familiar with this sort of site.
Lets say that they sell a variety of components.
On the entrance page would be the usual company information and an introduction to the site. The main function of this page is to act as a jump station to an index of the all components they sell. On this page use general industry keywords but this isn't a real important page for search engine placement for the site because you are trying to funnel the traffic to this page. Just be sure that the navigation on the subsequent pages have links to this page and all other subsequent indexes. Use targetted links to each component category.