This wooden edge slicker is used in conjunction with Gum Tragacanth to smooth and polish the edges of thick leathers.
To use, first apply gum tragacanth to the edges of your leather with a Wool Dauber. Hold the handle of the slicker so that the edge of your leather is in one of the grooves, then rub back and forth to smooth the fibres and produce a polished edge.
There is an alternative method for smoothing your edges, where you apply Gum Tragacanth and then pull your strap repeatedly through a woven cotton cloth, but it's still best to remove the sharp corners with an edge tool first.