Flexibility of traffic control during and after business hours is offered by 4510 Series Deadlatches. A reverse turn of the key while bolt is held retracted retains the bolt to allow two way traffic for hospitals banks and other buildings which require free entrance at certain times and exit only at other times. Interchangeable without stile modification with any MS1850A or MS1850S deadbolt of same backset and faceplate shape. They do not however provide the same maximum security level as the MS...