But in fact, they're not intended for folding bones;  rather, it is a tool made from bone  designed to crease and fold paper. 

That's not what we're using them for in laundry.  What we're using them for is to work stain removal liquids into fibers without the risk of altering the texture like a brush might.   Just apply a few drops of your solution to the problem area, and use an appropriate part of your bone folder to press it through the stain.  Typically, one works from the back and presses the solution and hopefully the stain into an absorbent white cloth. 

If you ever watch a dry cleaner at work, you'll typically see them use these exact tools for precision spotting and color correction work.  It's $10 well-spent.

Ecohu Bone Folder Set

Note that this product is made of natural cattle bone and should be cleaned before use following the package instructions.  If you're not using petroleum solvent like CRC Brākleen , the Fiskar's plastic bone folder is also appropriate.