The Emtek #3 Wrought Steel Double Cylinder Deadbolt has a keyed cylinder on the outside as well as on the inside. This type of deadbolt is generally used on doors that are part glass so that if an intruder breaks the glass, they would still need a key to unlock the inside of the door. It is not recommended on most doors because it increases the danger of a person to escape in case of a fire. Emtek Wrought Steel door hardware is made of solid steel for a heavy feel and lasting quality.