A bone folder or bonefolder is a dull edged device used to crease material in crafts such as bookbinding

Bookbinding

Bookbinding is the process of physically assembling a book from a number of folded or unfolded sheets of paper or other material. It usually involves attaching covers to the resulting text-block.-Origins of the book:...

, cardmaking

Cardmaking

Cardmaking is the craft of hand-making greeting cards. Many people with interests in allied crafts such as scrapbooking and stamping have begun to use their skills to start making handmade cards. This has contributed to cardmaking becoming a popular hobby....

 and any other craft where a sharp crease is needed. It is also used for marking fabric where a temporary mark needs to be made without damaging the material. Often made from the leg bone

Leg bone

Leg bone can refer to one of the following:*Femur - the thigh bone*Patella - the knee cap*Tibia - the larger of the two leg bones located below the knee cap*Fibula - the smaller of the two leg bones located below the knee cap...

 of a cow, deer, or similar animal (hence its name). There are also synthetic alternatives available made from plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

s. Bone folders made of Teflon have the advantage of not creating shiny marks on paper during use.