You don't need to change the locks when an employee leaves. By programming unique fingerprints into the 15-User Fingerprint Deadbolt Lock, you can be sure the only the people you authorize will be able to gain entry to your home or business. Four AA batteries are required to use this door lock and are sold separately. The 15-User Fingerprint Deadbolt Lock can be installed on either right- or left-hand doors. The Fingerprint Deadbolt Lock will accept up to 30 fingerprints in its system, providing keyless access to your entire family or your small business. It is recommended that you program two fingerprints from each authorized user. This lockset is designed to fit any standard wooden door that has installation holes for a deadbolt, but a template is provided for doors without existing deadbolts, as well. Programming is easy, and the LED display provides added convenience for programming and user management. Mechanical keys are included for emergency entry should the occasion arise. After correctly matching your fingerprint to the one programmed into its memory, the lock body is unlocked, and the system will power off automatically to save electrical power. If the batteries become low, you will hear four alert beeps when the lock is used. Replace the batteries as soon as possible; the Fingerprint Deadbolt Lock's non-volatile memory will retain all enrolled fingerprints and other setup functions. The 15-User Fingerprint Deadbolt Lock is also available in silver.