To install foam gaskets under light switch plates and outlet covers you will need a screwdriver. Installing foam gaskets under light switch plates or outlet covers on an outer wall is a great way to stop air leaks in your home. First, use your screwdriver to remove the light switch plate cover. Install the foam gasket by placing it over the light switch. Next, replace the light switch plate. Return the screws to their original positions and tighten the screws with your screwdriver. Follow the same procedure for your outlet covers. Installing foam gaskets will keep heat from escaping from your exterior walls.