Take a look at Dave's tutorial again...you will notice that he does make reference to using a liner to cover the inlay...it is essential to line the back of the inlay, especially if you are using a pad of some sort to make the inlay looked raised. If you are carving the inlay into the leather without cutting a complete window then a liner is not necessary. Take a look at Jay Fisher's sheaths, he carves all his inlays...very time consuming but they are beautiful.