64 Impala SS- What part is this please?

I have a part that came with the '64 Impala SS that I bought. It is approximately 24"x8". I think it is for the trunk- can anyone tell me exactly what part it is, please? (Then I can figure out where it goes!) Thank you!!!

Wait- is it a trunk to quarter panel filler? I saw sunbathing like it online.

By George, I think you've got it:

http://www.impalas.com/1964-impala-right-trunk-floor-to-quarter-panel-filler-panel.html

Thank you!!!