YOu can make a combined scabbard for both a knife and a hawk, but the extra leather adds to the total weight you are carrying on your belt, and prevents you from moving the two weapons apart for certain carrying conditions.
Some of the guys in my local gun club tried this years ago, but replaced the combination scabbard with individual sheaths after using the thing for awhile. All complained of the extra weight, and the lack of flexibility in how and where they carried the weapons. ( Sitting down can be a real problem for that fellow in the picture, for instance. Even if he removes the hawk and knife he still has that heavy knife scabbard sticking in the ground or his back :shocked2: when he sits. That's probably why he's kneeling, NO? :hmm: :grin: )