Dont know if this has been mentioned before (which it probably has) and i apologies if it has but......
Today a cleaned my car while it was my day off, Power washed all over and under the arches as best i could with only having a straight lance.
afterwards i ran a cloth under the lip of the arch to get any missed muck and was amazed at the state of the rag!!!
got a flat headed screw driver and scraped a lot of mud from in the corners and blasted it off again.
Then i see this little plastic cover:
I noticed it was a little loose so i bent it away from the arch to find......
this cover caught all the crap that runs down your arch and holds it there, helping to rot the end of your sills!!!!!!
needles to say i took the wheels off both sides and gave them a damn good clean and i will be getting it in the garage ond getting some q rust and underseal on them.