Pad lock is a relatively unusual lock key found on some keyboards with integrated numeric keypads. On most keyboards with an integrated numeric keypad, the keypad only provides numeric entry, and is enabled by pressing num lock.
On certain keyboards, including Cherry G84 Series keyboards with integrated pointing devices, and Zenith Supersport SX notebooks, there is an additional pad lock key. On a Cherry G84 Series keyboards, the numeric keypad layer is activated using pad lock instead. The num lock key behaves as it would on a desktop keyboard, in that it selects between numeric and navigation keypad layers.