When I first bought them I tried many different methods to prevent them from splitting during installation. I tried to tap very hard and tapped very softly. I tried to lubricate the tool and grommets. Nothing worked. Eventually I realized the "daddy" was too long and it broke as it folded all the way up and bumped into the "woman's" back. SOLUTION: Rub the nozzle on medium grit sandpaper. (e.g. 400-600 grit) and make sure it stays even and sands evenly. I found the figure eight movement to be helpful. - Stop sanding when the part only protrudes about 1mm from the underside of the leather to be worked - Attach the female part using the tools provided - Play around with different amounts of sanding until the end result looks good and gets cracks. 1mm overhang should be a good starting point, but may not be for everyone.