Walter, that's it! Thanks so much. I see now why my searches did not work. I did find this post in my slow reading through the site, but could not remember the subject line.
What has happened on my car, a '66, unknown history, is that on the "frame side rail" on the right side someone has brazed (brass or copper, it is a gold bead) a flat sheet at the bottom. It is welded on edge to the floor pan and front and rear edges are welded to the respective fender bottoms. On the outside it passes under the outside "rocker", the curved part under the door, as it should. To finish this repair, a rubber coating was applied along the crack between the welded plate and the curved "rocker". That was allowing rust to start on the rocker, so I'm pulling all that coating off. The crack that should be there is starting to be uncovered and rust can sanded and covered properly.
That area of the car is very strange to me. I've never seen anything like it.
Ron
