I designed this simple case for the Japanese Spear-Point Marking Knife (kensaki shirabiki) sold by Lee Valley: https://www.leevalley.com/en-ca/shop/tools/hand-tools/marking-and-measuring/marking-tools/110953-japanese-spear-point-marking-knife?item=60N0704

The marking knife came with a flimsy plastic cover to protect the end and given how sharp the knife is, it felt very inadequate! So I made this case! The case utilizes a simple living hinge, and the two halves of the case snap together securely. A thumb-pull makes it easy to open.

The inner dimensions of the case are 170mm x 18mm x 3.5mm. Outer dimensions are 180mm x 28mm x 6.5mm.

I've included the original Fusion 360 file. Since each of these marking knives are handmade and slightly different, you may need to tweak the dimensions. The entire model is parameterized, just tweak the variables to suit your needs and everything should readjust fine.

I recommended printing with PLA tough as its a bit more flexible and will result in a more durable hinge. I've also tested it with regular PLA and it should hold up just fine. 0.2mm layer height and 5% infill is plenty strong.