I would expect that you will find, when buying a kit for this device, that it will have instructions for installation. Primarily, it's important to determine the construction of the door. Some doors are hollow and others are solid. If the door is hollow, it's very important not to cut the bottom stile or rail. Additionally, it will, as Elvis suggests, require the cutting of a hole. Be sure to use a saw with a blade designed for cutting nails, since you may likely encounter one or more when cutting the hole. Always remember, whenever cutting with a saw, measure twice and cut once. Good luck!