There are access holes where the rocker molding attaches to the sheet metal. I plan to spray inside there when I do this.
Originally Posted By: eljefino
Despite your visible rust, rockers rot from the inside out. Best bet is to drill a couple holes in the door sill area (protected by/ inside of the weatherstripping) and spray an oily preservative of your choice down in there. Then cap said holes with little rubber/ plastic caps you can probably get from Lowes in the "weird fastener" bin. If you drill a 5/8 hole you might be able to get a camera lens and flash in simultaneously, to inspect the pending horror.