Typically found on home front doors, a nightlatch automatically locks when a door shuts.Operated by a key from the outside, some nightlatches can be double deadlocked from the inside and others from the outside. However, such products would not be recommended for properties that have a single entry point, such as flats and apartments. If ever there was an incident where the key could not be located, then it’s possible that residents could be locked inside.If a nightlatch lock features a Kitemark on its face plate, then this will have been tested to BS 3621 standards.