Well, in the
textures folder in the Soldat directory, there is a folder called "Edges" if you haven't noticed
. What you need is to find the texture you want to use, then either take an already made edge:
Copy and Paste, rename the edge file to the exact name of the texture you want to use or...
You can make your own edge, and do the exact same thing (renaming it the exact same name as your texture).
