Lots of experience, patience, steady hand and an ultra sharp Olfa blade. It may sound strange but the sharper the blade, the LESS likely you are to cut through to the paint. With a sharp blade you can feel when you are gliding in the poly layer and when you get into the 2 mil thick adhesive layer. All of my installers are practiced at this. Like us on Facebook to keep up with the awesome cars we work on. speedshieldusa on Facebook.