D tiller, i made a wooden sheath once. took 2 oak blanks 1/4 " thick, laid the knife on what would be the inside of each, marked it out, then chiseled away the wood until the knife would sit in nicely and the two slats would join with clean lines. After that, glue em together: just don't go crazy with the glue on the inside, cuz you don't want it to leak into the hollow.