What is this part, for an Ipad Air?

Hi all,

could somebody please help me out. My Ipad Air broke, i had to disassemble it, and although I followed good guidance on the net, things went wrong when I was putting it together again.

This is the part that I just can't figure out where it's supposed to fit in, and I can't find it in any of the guides either (Fixit, YouTube etc):

On the net, it is listed as several different things, but that's on eBay and such. A more credible source of information labels it as an "Interconnect PCB" here:
http://www.upgrademag.com/web/wp-content/uploads/2013/11/Apple-iPad-Air_Exploded -annotated.jpg

The print on the back says "821-1901-A" and "C 4313".

Any help would be much appreciated.