Typically, we think of a locksmith as someone who lets an individual get inside of a building when they are locked out. While this one role that they fulfill, they can also help keep people out of a building as well. Through access control locks, only those who have the right button or group of buttons to push will gain access to the building.
Those who own an apartment complex may want to install one at the entrance to each apartment building or complex community center. This ensures that residents can get into their building or use the gym while others will be kept away. Access control panels may also have a slot for a traditional key in case the door does not unlock after the code is entered.
If you own a commercial building, you don't want thieves or corporate spies to get into your headquarters and steal sensitive information. Only your employees or authorized management will be able to get into the building or access certain areas within it. For instance, you could have one such access lock at the front of the building with its own specific code and another put on doors leading to research labs or the CEOs office.
Access panels can be tailored to the needs of the apartment or commercial building's owner. In some cases, you simply push a button to unlock the door. However, it may be possible to require a key card or some other device in tandem with a password for an individual to gain entry. If the card fails or the password isn't entered properly, it may be possible to alert authorities or keep the door from opening for a certain period of time.
How Locksmiths Work, videos.howstuffworks.com