The door spies should ideally place in the centre of your front door. And before you proceed with the installation process, make sure you choose the correct size of peephole viewer for your door. First, you need to mark on the door where you wish to place your viewer. And make sure you choose the appropriate flat wood drill bit tool. But don’t forget to check regularly while drilling on the other side of the door. To make sure you don’t damage the door. Next, you need to use the door stopper to stop the door from moving while you drill on the other side of the door. Now, unscrew the two parts of the door viewer. Place the lens one from the outside and insert the bio from inside. And make sure you place it properly.