Things You'll Need
1/4-inch drill bill
Spade bit or hole saw
Installing a peephole, or door viewer, in your fiberglass exterior door is an easy way to add an extra measure of security to your home. Fiberglass doors are actually two fiberglass panels with wood and an insulating foam core between the panels. You can drill through the fiberglass and the core to install a peephole. Some peepholes have tiny "teeth" around the viewing lenses, which are meant to be pushed into a wood door during installation. Avoid buying this type of peephole for your fiberglass door. If you already have a peephole like this, it will be necessary to break off the teeth to allow the lenses to lie flat against your door. Standard peepholes are very inexpensive but offer a limited viewing area. Wide-angle, or security, door viewers cost a bit more, but allow you to see a much greater area when you look out. They also have a wider viewing area from the inside, meaning you don't have to stand right up to the hole to look out, and people of different heights will have an easier time looking out the hole placed at one level.
Purchase a door viewer. Choose the correct size drill bit based on the recommendations printed on the door viewer's packaging. Standard door viewers typically require a 1/2-inch spade bit to drill the hole, while large, wide-angle viewers might require a hole saw of 2 inches or more.
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Decide on the location of the peephole. They typically are placed in the center of the door. Choose a height that is accessible to all of the people who will be looking out the peephole. After deciding on the height, measure the door's width and make a pencil mark at the center, where you will drill the hole.
Use a 1/4-inch drill bit to drill a pilot hole into the fiberglass panel from the inside where you marked the hole. Being sure to hold the drill level, continue drilling through the core and through the fiberglass panel on the exterior side of the door.
Change to your larger drill bit. Put the tip of the spade bit or hole saw into the pilot hole and drill your peephole. Stop drilling when you feel the drill bit begin to press against the exterior fiberglass panel. From the outside, place the larger drill bit into the pilot hole and drill through the exterior panel.
Untwist the door viewer to separate it into two sections. Insert one section into each side of the hole made in your door, being sure to place the lens so that the viewer is on the inside and the lens that shows the viewing area is on the outside. Twist pieces together to tighten.