A bone folder is a tool often used in paper crafts such as Japanese origami (artistic paperfolding), scrapbooking, and card-making. A classic bone folder is carved from real animal bones, often deer or elk. Bone is an ideal material for paper crafts because it is sturdy, smooth and grainless. Many bone folders are carved with ornate handles or other decorative features, but a basic bone folder is typically shaped like a wooden tongue depressor or a large popsicle stick. It may have rounded ends or a pointed end for working in corners.

There are a number of uses for a bone folder, including folding creases, burnishing decorative papers and scoring paper stock. Many crafters use a bone folder as a means of giving a folded page a more professional-looking crease. The friction between a finger and paper may create problems over time, but a bone folder's smooth surface can be drawn across the fold time and time again. The bone material allows the crafter to apply constant pressure while finishing a crease.

Another function of a bone folder is called burnishing. The bone folder's smooth finish imparts a glossiness or shininess to paper as it is drawn across a fold or crease. Burnished decorative papers often present a more professional finish than unburnished papers. A bone folder acts much like a polishing stone, smoothing out the paper's fibers and creating a more defined fold.

The straight edge of a bone folder also makes it ideal as a paper folding aid. The crafter can hold the bone folder against a scored line and fold the paper along its edge. The pointed end of a bone folder can also be used to square off a corner from within the folded area. This can be a difficult task to accomplish in the more elaborate folds of origami projects.

The edges of some bone folders are also sharp enough to score paper. This can be a blessing or a curse for bone folder users, depending on the project. Excess paper can be trimmed away with a straight edge and a sharpened bone folder if desired. Paper crafters must be careful not to puncture or slice through a project with a bone folder accidentally, however.

A basic bone folder can usually be found in hobby and craft stores, scrapbook supply stores and online craft stores. Bone folders are sold in different sizes and shapes, so look for one that suits your creative needs and fits well in your hand. More ornate bone folders may be available at professional carving outlets or through custom order. Materials such as horn, stone and even Teflon® are also used to create paper folders, so it helps to read product performance reviews before investing in professional-level art tools.