I do have a Nissan Tonneau Cover. I'm crap at DIY and don't own one electrical diy tool so making one is out of the question for me. As stated they help to keep the cabin area a bit quiter and keep things hidden in the boot.
If like me you are poor at DIY, you can still get these from Holdcroft, a Nissan trader on here who will do them at discount. You will need to contact a admin/mod for a discount code. Check out the forum discount section for more information on Holdcroft.