Press the "Num Lock" key to activate the numeric keypad on your keyboard. You cannot type ASCII symbols from the regular line of numbers at the top of the keyboard.

We went in search of the best keypad door locks to find models that are secure, easy-to-install, and easy to use. Here's what we found.

Evgeny Katz and colleagues describe development of a chemical "keypad lock," one of the first chemical-based security systems of its kind.