Just in case you are not familiar with the structure of your Jaguar, this piece is hidden behind the Front wheelbox liner, where the sill projects forwards of the toeboard. If you look closely at this part you will notice that not only is it curved to fit snugly into the shape of the sill skin (which is partly why Jaguars rot here), but it also tapers to match with the curve of the of the front wing eyebrow!