About 18yrs ago, I decided to replace my car. Trouble was, I couldn't find anything that appealed. My then current car was getting a bit long in the tooth so I sold it on. I was offered a VW Polo which I used for a while. One day on a single track road with passing places, I reversed into a passing bay and ran the nearside rear wheel over a lump of concrete. I was on my way home, it was dark, and I just gave a cursory glance. No noticeable damage, so I carried on. Next morning I agreed to take the wife shopping, and as she opened the rear passenger door to put her bags on the rear seat, she told me it didn't look right. On inspection, I found the outer sill, floor pan and quarter panel had all separated due to severe internal corrosion. The impact with the concrete had done the damage, but it was damage to the wheel arch liner that had allowed an accumulation of dirt and water to sit festering away long enough to cause the corrosion. Since then I have periodically checked them on all my cars, but I wonder; when was the last time you checked yours?