i have made several sheaths out of backplate webbing, just take a piece of webbing and fold a belt loop in it and sew it down, the then take the other side and fold it up forming the sheath part and sew along the sides. Depending on the size of the knife the size of your webbing ,the tight stiching, and extra stiff webbing will be all that is needed to hold your knife in. No other retension. I cannot get mine to fall out, but it draws easy when i need it. For these KA-Bars the regular 1.5 inch webbing is the perfect size just sew right on the edge for a tight fit, if you knife is a bit slimmer you might trim the webbing thinner or sew a little more into the edge. On the sheath portion, don't sew quite all the way to the bottom and the water will drain easy and you can put a boot lace through it to tie around your let to secure it to your leg if needed for field use. You need a heavy sewing machine for this though!! ( prob the kind built into a table) as you will bust needle's and thread right from the git go with a small machine. I have a 5 HP old singer. It will also be easier on your machine and to bend and fold if you soak the webbing in hot water, its alot easier to work wet. Here is some pics.
kurt
ps the one on the top has a angled belt loop for a cross draw, i wear it on my left so it lays back and stays out of the way and can be drawn with either hand. The bottom one i can wear on either hip and hangs strait down.
