I’m working on putting back my 01 f-150 supercrew cab. On top of the cab there is this seam which runs the length of the cab top and is where the cab is welded to the uniside of the truck. The welded seam is hidden by this rubber type material which has been filled and painted. To look at the rubber seam it looks like steel but when you cut into it, it’s like rubber. Photo of the top of the Cab Seam revealed . After I weld back the spot welds I then want to put back that substance so I can prep for painting. Can anyone from the photo tell me what type of metrial that is so I can buy it?