This bone folder (its actually made of plastic, but still traditionally called a bone folder!) is used to smooth and polish the edges of thick leathers, and to achieve neat folds in thinner leathers, card and paper.
To use for polishing, apply gum tragacanth to the edges of your leather and then rub with the bone folder to flatten the fibres of the leather and produce a smooth finished edge. (This technique only works on stout leathers with a solid edge to rub against - we don't recommend that you try and burnish the edges of soft, lightweight leathers)
This is a two piece tool with a removable end section which can also be used as a burnisher, in a similar way to our burnishing wheels.