how to 'mount' an ATR file in SDX

In a few topics I read that SDX has some kind of ATR handling. If I understand correct you have a ATR file already on your SDX harddrive, and in some way (I don't know how) you can 'mount' this ATR so the atari handles it like a real existing floppy/partition.

If I understood it wrong... please let me know that too.

I have this tool on the SDX Toolkit disk, named MKATR which creates empy .ATR files on my harddrive.

I would like to use these .ATR files now like small partitions, etc.

In the IDE+ thread I asked it twice, but I'm afraid my messages are lost in the discussion about the IDE+ interface, so I will ask it here in a new topic.

If there are any other tools or drivers needed, could someone upload them here, of point me in the right direction?

Thanks a lot
M.