Aye the pouch is for a folding knife! Can't find my super glue though..and I don't fancy opening a brand new araldite extra strong.
Not all boot carry is neccessarily concealed. As pointed out earlier a Daniel Boone style with an ordinary outdoors type knife on the outside of the boot would be quite as visible as a belt sheath. On the other hand a pouch such as Samon is describing would probably hold a folder and I'm not sure how that would really be any more concealed than if that same folder were carried in your pocket. Just trying to get away from the short dagger image that the word "boot knife" tends to conjure.