This invention involves a security lock for a door hinged on a first door jamb for swinging between an open position and a closed position in which the door is positioned between the first door jamb and a second door jambs. The security lock comprises an elongate locking member mounted on or adjacent the second door jamb in an upright position wherein the locking member has a substantially continuous vertical surface extending at least a substantial portion of the full height of the door, and an actuator mechanism for effecting lateral movement of the locking member when it is mounted on or adjacent the second door jamb from a retracted position in which the locking member is clear of the door for permitting the door to be swung open from its closed position, to an extended locking position in which said substantially continuous vertical surface of the locking member overlaps a marginal portion of one face of the door to prevent the door from being swung open, the overlap between said locking member and said marginal portion of the door being substantially continuous along at least a substantial portion of the full height of the door.
