I've been having rats getting into the passenger compartment for a long time...
First I put hardware cloth over the HVAC intake. That helped for a while, but then they came in again. WTF?
I finally figured out where the rear vents are and sure enough, it was the grand entrance!
Note: there's a vent on each side, you can access them by pulling back the fenders as shown, and there's only one non-obvious bolt shown in the photo with the wrench.
I'll let the photos speak for themselves...