when i bought my car it came with a hatch cover. whats strange is that i dont appear to have any place when it would screw in. it looks like it has a lock which doesnt seem to have anything to lock to. i think this peice belongs to another car and somehow found its way into my trunk. anybody have any ideas?

We could have a better idea if you posted a pic, or gave a better description of it.

It sounds like you've got a factory cargo door but maybe your car didn't originally come with one. There should be holes in the floor to mount it. Also, cargo door cars had a slightly different rear plastic panel. Those panels had a small ledge for the cargo door to rest on and also a spot that allowed the door to be locked close.