I have been fixing up my van. Removed the headliners today to reupholster them. I removed a side panel to replace a dead speaker and I found this carpet padding back there. Is this stock? I'm assuming it's for insulation and or sound dampening but it doesn't seem to be attached to anything so it's just sitting in a pile. It's the same behind all of the panels. Should I glue it in place?

 

That is for sound proofing. Go to Home Depot or most any hardware store and pick up a can of 3M spray glue. With it you spray the backs of the panels and then stick the padding to it. This is preferable to gluing the padding to the metal body panels, just in case body work ever needs to be done.

 

^^^^^^^^^^^agree^^^^^^^^^^^

 

All in agreement with above. I would also cut them short so there is nothing down in the bottom of the cavity to absorb moisture and exacerbate rust.