Underneath my 2003 f150 there is these bracket type looking things on each side. they appear to connect the body to the area where the rocker panel end. There are a few on each side. See attached brackets. one on each side is totally rusted out and I am looking for the part name in an effort to search forums and internet on how to repair (or decide if the repairs are even needed).

Thank you

 

I have always called them "Crossframe members? Usually the transmission, is mounted to them, or maybe the truck bed.
Upon 2nd look at your picture I realize they are not what I thought. Looks like where your body attaches to frame maybe.