I believe the knocking sounds are the "Ghost of Lot Lizards Past" some say to just throw a $20 out the window and they will leave you alone.
The lot lizards seem to be ignoring me a lot lately. I would never touch one but when I see my student get approached by one then she walks by me and doesn't say a thing I get a little offended.
That's just because she can't. It's not easy pulling all that weight up out of a chair ya know. Have a little compassion.
Happens here too, sometimes I gotta get and look and scratch my noggin.. hmm I'd like to think its just everything settling, be careful what you wish for Dewey120
After a few hours, my air pressure leaks down to the point where the cab airbags deflate. The whole cab / sleeper starts creaking and moaning when that happens. The first time it happened, I jumped up from a sound sleep and headed out the door with my tire thumper. Took me a while to go back to sleep hehehehe.