Smart locks allow you to use biometric, pin code, key card or facial recognition to unlock the door. Most even have a manual key option in built so that you can always use a traditional key in case you need to. They work on batteries so they do not fail if the electricity dies and they also can be used to unlock the door remotely from an app if you know who is at the door and want to let them in. They are very safe and effective and allow you the flexibility not to have to carry keys everywhere you go. Access can be easily removed or added directly from your smartphone app and guest access can also be given if you want to give someone temporary access to the door.