Abstract: Mechanism for securing a door in open or closed position comprises a casing which is secured to the inside of the door near the bottom and has vertically aligned openings to receive a vertically movable hollow cylinder. The cylinder is biased upwardly by a helical spring in the casing, upward movement of the cylinder being limited by a plate which is affixed to the cylinder and engageable with the upper end wall of the casing. A plunger which is reciprocable in the cylinder is biased downwardly relative to the cylinder and is held in an upper or retracted position by a latch provided at the upper end of the cylinder. When the latch is released, the plunger is forced downwardly by its spring into engagement with the floor or with a socket set in the floor. When the cylinder is pushed downwardly far enough for the latch to engage the plunger and is then released, the cylinder and plunger are moved to their upper positions by the spring acting on the cylinder.

Abstract: A flush bolt mechanism is disclosed for latching the inactive one of a pair of swinging doors, the mechanism functioning to latch the closed inactive door in response to closing of the other door. The latch mechanism includes a bolt that is driven home by cam and spring assemblies. A heat-responsive mechanism is provided for retaining the bolt in its extended position when the heat-responsive mechanism is subjected to a temperature and for a time sufficient to melt one of its components. A release mechanism may be provided for retracting the extended bolt in response to a force of preselected magnitude applied against the inside of the inactive door.