Dock Adapter in iPod Classic Box--What Is It Good For + non-video iPod Doc?

I bought a 160 gig iPod Classic yesterday and it came with a small dock adapter (looks like a snap in type item). What is it for? I looked at the dock for my iPhone & the dock for my non-video 60 gig iPod (can't remember which generation--it's color display & does pictures), but the adapter did not work in either dock. Is it meant for docks like the Bose Sound Dock?
boldSecond question: bold I tried using my iPod dock with the iPod Classic, but it did not work--it felt like it was loose. Does anyone know of a way to get a dock to work with the iPod Classic?
TIA,
Amy