Name that part and you get....well you get a pat on the back

4404spd is correct. Trunk hinge, it slides into the square open end, that end is then slide into the trunk lid and the lid fastened to the hinge. This is where you need a pic and I don't think I have any...
I also think it is missing a clip of some sort that holds it in place... Do you have any funky clips that you don't have a home for yet?

At what stage are you in the re-assembly? Pics?
C