Abstract: A non-key operated lock for the door of an occupied room comprising a vertically elongated prop member pivotally mounted to a guide member at its upper end for oscillation about a horizontal axis for movement between a first inoperative downwardly and outwardly inclined position with the lower end of the prop member spaced above the lower marginal edge of the door and a second operative position with the lower end of the prop member swung toward the door and projecting at least slightly below the door lower marginal edge for engagement with a horizontal surface, such as a floor, over which the lower marginal edge moves when the door is moved toward the open position thereof.