Fray check is a liquid seam sealant that prevents fabric from fraying and secures the ends. Withstands repeated laundering and dry cleaning. … Gently squeeze the bottle and apply a very small amount of fray check.
Even pleather and cork have a canvas backside. It is possible that a thread will hang loose. You can fix this with fraycheck. It’s not needed for the stability of your work. If it bothers you, fraycheck to the rescue.