Thanks Cattleman, after the sheath is done I dip it in water for about 5-10 seconds they open it a little with my fingers and push the knife in. once it's in where I want it I put in in a heavy plastic bag, pull a vacuum and form it real good with a piece of polished antler. I really don't think the vacuum is needed for knife sheaths but I use it anyway because it's available, then take it out and leave the knife in for about 20 min. pull it out and put it in a PID controlled toaster oven at 150 for 45 min. or so, flip it and leave another 45 min or so. it comes out hard but still has some flex on the sides.
The hopeful part for me is going in the first time, I put a hump, or cam in the welt that the finger choil rides over then snaps into the sheath, this one worked out good but sometimes I have to use a partially taped up rat tail file to lower the cam point so the knife will get by it.