Abstract: A locking structure for use with a door equipped with a latching member capable of being linearly moved in latching and unlatching the door can be constructed so as to utilize a control part secured to the latching member. Openings are provided in the control part and in the door in positions in which these openings are aligned when the latching member is in a latched position. A lock mechanism including an end flange may be inserted through the openings when they are aligned so that the flange fits against the exterior of the door. This lock mechanism includes a movable retainer which can be moved by appropriate actuation of the lock mechanism so as to extend outwardly from the locking mechanism in such a manner as to engage the control part. When this retainer engages the control part the locking mechanism is secured in place in such a manner that the latching member cannot be moved so as to unlatch the door. A protective structure is preferably used on the door around the opening within the door.