I looked around on the net for a manual or instructions and the best I could find was the what Lars is saying. (mount tube to lens first)

I have additional issues because I have a 645 AFD and was wondering what could be mixed and matched.

You can mount a manual lens on a AF/AFD body and use stop down metering and manual focus so can you use M645 manual tubes with a manual lens on a AFD body? It seems you should be able to.

I cant even find the correct way to mount the m645 tube to a m645 lens. There is the stop down lever that tkamiya mentions then there is the metering coupler prong like Nikon uses.

Anyone know where I can find some decent instructions. Butkus.org came up with an accessories brochure but that doesn't contain and instructions on the dos and don'ts.