How to best interface with ext DLLs?

[Brett Romero]

I'd like to build a layer in all applications that interface with
certain DLLs, of which I know and have source code access too (along
with compiling). The layer will abstract the DLLs. This keeps the
application from directly accessing anything in the DLLs, except at
this layer. The layer will simply be a class.

I'd like suggestions on any certain patterns that come to mind, use of
interfaces or abstract classes. I don't see how an interface is needed
on this layer, as I will always know which DLLs are being used.
Additionally, the DLLs will be to different for use of an interface.
Similar situation for the abstract class. However, I'm open to
suggestions.

As an example, I have one error handling DLL and one configuration
(server and DB names, etc.) DLL.

Thanks,
Brett