If you have a door lock that is activated with solenoid, then probably you would like to have a keyless access. This can be done easily with Arduino, keypad, LCD and relay which activates lock mechanism. Praveen has shared a second version of code lock he built. In previous version he simplified too many things like, no LCD, hard coded password. This time he wanted to make things better and included all missing parts.
During initialization, user is prompted to enter a password which also can be changed later. Using LCD made it much easier to enter passwords navigate menu and debug program itself.