The bone folder I'm familiar with actually comes from kimono making.
When hand-sewing kimono, because it's mostly straight lines, you
traditionally zig-zag the fabric onto the needles to make numerous
small, straight stitches in one go. You then use the curved part of
the bone folder to create firm creases without damaging the fabric (as
irons weren't used much), and the pointed bit to turn corners inside
out, such as the bottom of the large sleeves. Not sure when Japanese
folders saw the usefulness of these for origami, bit it at least dates
back to the 80s, and provably much earlier.Clare, Perth Origami Group
