Bonefolder

A bone folder, bonefolder, or folding bone is a dull-edged hand tool used to fold and crease material in practices such as bookbinding, origami, and other book arts that require a sharp crease or fold.

Teflon bone folders will not glaze materials (make shiny) as genuine bone will, and may be preferable for delicate materials or applications where that effect might be noticeable.