Intruders do not only come when you are out of home. Besides break-in protection retrofit security technology has another crucial advantage: It offers protection when you are at home and can protect you against robbery at your door as well as frauds or dubious salesmen.
Bolt locks and additional door locks which are equipped with stirrups allow you to open the front door a few inches for example. This is perfect for accepting smaller items or a short talk with a stranger.