Our customer needed access to the second-floor bedrooms, but wanted to be able to lock the unit when her grandchildren visited. Harmar's lock-out option is key-operated (the key is located on the chassis of the unit), and easy to use. The key can be stored when not needed, then the unit can be locked when the munchkins visit! Also to note...the state of Georgia does not mandate that an overrun of track at the top of the stairs be a certain length, but a 7-inch span is a good general rule. We have a happy customer whose home is now safe for the littles!