Fitting a spy hole allows the home occupier to look out without the person outside looking in. The fitting is incorporates a simple lens system, which offers a wide angled view of the surrounding outside area. It is particularly useful in conjunction with a porch light, to enable clearer vision when it is dark.
Decide on the most convenient height for the spy hole. It should be installed so that all members of the household can use the facility. Drill a hole for the spy hole, and, by holding a spare block of wood on the other side of the door, you will stop any splintering of wood as the drill bit passes through. Attach the two sections of the spy hole on either side of the drilled hole and secure the position of the fitting following the directions of the particular type used.