With some scraps from a remnant bag I made this headknife (round knife) sheath. First I carefully traced around the head of the knife on a file folder, then enlarged the pattern with a compass (dividing tool with a pencil on one end). I made the outter sides out of black 8-9oz. smooth and stiff leather, and a skive tapered gusset out of what started out as 5-6oz brown leather. I didn't want to use any metal that may mar my knife, or worse knick my edge, so I decided to use the top edge of the gusset to hold the blade in place. I used contact cement to place my tapered gusset in place, then stitched one leg of the top edge of the gusset to the back side. Next, I place the front side on and stitched the remaining gussetted area through all three layers. Since the gusset is only attached to one side of the front, and both sides of the back, I can slightly squeeze the top points of the sheath together, opening the half-free side and pivot the knife in place. At no point inside the sheath does the knife's edge contact the gusset nor stitching.
Joel