[Spurious]

Minor rust can develop under the rubber on the A pillar next to windscreen. Leaves etc... can fall on to roof, move to the gutter & get stuck on the way down.

Also having just removed my tailights I found a fair amount of hardened crap stuck under the top outer edge of the unit along with more of the same under the unit on the body with a trail between the 2.

Also when I repainted my car I removed the mud spats. In doing so I found a whole heap of dried up mud etc...jammed up in the sill behind the spat (behind the plastic sheath on the wheel arch). I left the spats off after repaint so I can regularly Karcher these areas.

The vent in the boot (left hand side quart panel behind plastic panel) had let in a whole heap of road dust.
With age the rubber flaps in the vent don't seal properly. So I wrapped the unit in some cloth (toweling).
I also found some open holes in the boot floor pan. Don't know why or what went through them but I blocked them up with liquid nails & some small squares of plastic.