Guys I need help (not that sort

)
I know the basics ie Hood = bonnet!
I'm trying to find a replacement part but unsure what you guys call it!
In the UK we call the inner and outer sills. Its the curved panel you see that runs the length of the cab under the doors that welds up to the bottom of the door opening. So if you are sat in the cab, opened the door and put your left hand down its the curved panel that runs underneath.
Any help please as I'd rather replace in full rather than weld plates over the rusty bits!
thanks
Andy