The pre-mask is a translucent layer on top of the vinyl which allows the kit to retain its shape when you place it on a vehicle. You squeegee the kit right through the pre-mask layer and pull it off when the kit is completely squeegeed onto the vehicle. If you are doing a wet installation, wait at least 15 minutes before removing the pre-mask layer. When you remove the pre-mask, pull evenly and slowly, back at a sharp angle to avoid lifting the kit. Using your spray bottle, you can wet the top of the pre-mask to soften it to aid in removal.