There will come a time when you want to secure something in your project. You could use a keyswitch but what happens when your key is lost though? Using a keypad allows you to have as many codes programmed as you want and change them at any time. If you are thinking of adding a keypad to an Arduino project have a look at this Arduino Keypad project for some inspiration. It was made by Paul-Arthur Asselin who is 15 year old Hacked/Maker!
“The buttons on this particular keypad are setup in a 3X4 matrix format so we only need 7 pins to detect the pressing of 12 keys. For example, when you hit the number 3 pins 5&2 are connected, 6 connects pins 5&7 and 9 connects 5&6. So in code we just look for the combination and we know what button is being pressed.”