A door viewer is an easy way to see who is on the other side of the door without opening the door. Peep holes are relatively inexpensive and very simple to install.

Step 1: Choose a door viewer with a wide angle to optimize the view on the other side of the door. Viewers come in a host of colors and styles; select a color and style that complements the door it will be installed in.

Step 2: Read the viewer instructions and purchase the correct size drill bit for the job. Choose a brad point or paddle bit for wooden doors. Choose a regular drill bit for metal or fiberglass doors.

Step 3: Determine the optimal height for the door viewer. Viewers should be installed at eye level. If there are several people in the home, install the viewer at a height where both the shortest and tallest person can use it. For homes with substantial height discrepancies, consider installing two viewers in the same door.

Step 4: Use a tape measure to determine the center point of the door width. Mark the spot where the desired viewer height meets the center point of the door width.

Step 5: Drilling straight though a wooden door can splinter the wood. When installing a viewer in a wooden door, hold the brad point or paddle bit up to the side of the door and mark the thickness of the door on the drill bit with a piece of tape. Use this as a depth guide when drilling.

Step 6: Use a power drill to drill the appropriate-sized hole through the door. Hold the drill level to ensure the hole is straight. For wooden doors, drill through only as far as the depth mark on the drill bit. Back the drill bit out of the door and finish drilling the hole from the opposite side of the door, using the hole made by the drill point as a guide.

Step 7: Use sandpaper to smoothe the edges of the viewer hole and clean away any debris.

Step 8: With the door opened, insert the viewer portion of the peep hole into the exterior side of the door. From the interior of the door, screw the eye portion onto the viewer portion. Use a coin to finish tightening the viewer assembly from the interior side of the door.