The sheaths were made with the rough side out. You put the sheath and Bowie knife inside a sash or belt, and the friction between the two items kept them in place. The polished, or ' smooth" of the leather allowed the knife to be pulled from the sheath, quickly, without pulling the sheath out of the sash or belt.
Today, a lot of men make their sheaths with either a slot( or 2) to put a belt through, or a long supported leather "hook" that hooks over a belt, and keep the sheath from falling down through between the body and the belt. Some use the more modern design of a Loop sewed to the back of the sheath to hand the knife from the belt, on the OUTSIDE.
I found to my detriment that hanging a large heavy knife from a belt look beats your upper thigh to black and blue bruises in a day of walking around, and have since carried my knife higher behind the belt. I was very young, then. :idunno: :shocked2: