Patent ID: 7165595

Claim:
A security door apparatus that is openable and closable with respect to one side of a door opening frame, the security door apparatus comprising: an entrance door; an upper horizontal slide guide and a lower horizontal slide guide disposed on one of an inner side of the entrance door or on a side of the door opening frame; a rectangular-shaped auxiliary door having a width that is smaller than a width of the entrance door, the auxiliary door having an upper and a lower corner on a first side connected to the horizontal slide guides disposed on the one of the inner side of the entrance door or the door frame opening frame, and an upper and a lower corner on a second side connected to a side of the entrance door or the door opening frame not having the horizontal slide guides, wherein the auxiliary door is mounted on the entrance door and the door opening frame so that, and when the entrance door is opened, the auxiliary door forms a barrier across an opening between the entrance door and the door opening frame, thereby preventing a person outside of the auxiliary door from entering through the opening; and wherein the auxiliary door has multiple openings formed so that a person inside the auxiliary door can visually confirm an the person outside of the auxiliary door through the openings in the auxiliary door.