Everyone asks what this is when they first see it. My first exposure was in the 70s when I saw copy clerks folding oversized blue prints. The bone allows you to add a crisp, flat crease to paper which in the case of large prints means a neater fold and less volume for the file cabinet. My wife uses it for gift wrap.

Google folding bone or bone folder.

You don’t have to use my STL file since this is so easy to create from scratch. The difference between an official store-bought bone and one done in PLA is that PLA is a softer material and is less stiff. With the dimensions I chose it comes very close to an official bone. My design is approximately 190mm long, 23mm wide and 5mm thick. I applied a maximum radius to both the top and bottom face.

After printing spend 10 minutes hand sanding. Start with 60 or 100 grit and move up to 1500 or higher grit.