Installing a deadbolt adds an extra level of security to your home. To drill in a fiberglass door to accommodate the lock and deadbolt latch, you'll need special hole saws designed for fiberglass. These hole saws look like small barrels with three notches. The end of each notch has a tooth that cuts evenly through the fiberglass. Three tooth hole saws and the other materials required to drill in a fiberglass door are available at specialty hardware shops and home improvement centers.
Mark the area on your door where the holes need to be according to the directions in your deadbolt lock kit. Most kits include a template that you tape to the door.
Place the tip of a center punch over the center of the template holes and tap the end of the punch with a hammer. This prevents the pilot bit from "walking" when you first begin to drill.
Thread a mandrel into the back of each three tooth hole saw. The mandrel holds the pilot drill bit and threads into the hole saw in one way.
Insert the drill bit into the mandrel through the tooth end of the hole saw. Push the bit through the mandrel so there is only 1/4 inch of the bit extending beyond the tooth side of the hole saw. Tighten the set screw on the side of the mandrel with a flat-head screwdriver to secure the bit.
Install the hole saw into your drill just as you would a drill bit. Begin drilling at the center mark of the template on the door from the inside of the door. Use slight pressure and even speed when drilling through the fiberglass skin.
Continue drilling when you get through the fiberglass skin and into the foam inner filling until the pilot bit exits through the opposite side of the door. This provides a pilot hole on the other side. Stop drilling and pull the drill out of the door.
Go to the opposite side of the door and drill at the pilot hole. Apply light pressure and steady speed until you drill through the door. Pull the drill out and change hole saws to drill the edge of the door for the deadbolt latch.
Drill the deadbolt latch hole through to the main hole.