How does the rail system in cargo area work on the 2005 Pontiac Vibe?

there should be a plastic bag in the spare tire area (under the back plastic door) that contains little metal "nuts" and plastic tie down "screws"- put the nut down in the track and then screw the tie down down into it until it is tight and then you can tie stuff to it. if the bag of stuff is missing, you can get them at a gm parts dept. at a gm dealership.

Thanks. I think the plastic tie down "screws" are missing--will check again.