Before you begin
This guide helps to replace the normally flexible, felt lined rubber and metal trim which sits against the bottom of your window and seals it against rain as well as wiping water off it if you open the window while wet. These items get brittle and peel backwards as they age, resulting in water falling off the window directly into the door cavity and starting to rust things. It's particular important on the drivers side, because the wipers push water off the windshield during rain storms and onto the drivers side door window.