These double cylinder, heavy-duty entrance Mortise lock sets are constructed of various materials and come in a polished brass finish. They are designed for use on exterior entry doors, engineered to match the vintage hardware used on the interior doors, without jeopardizing the security of your home. These security lock sets can be installed on entry doors ranging from 1-3/8 in. To 1-3/4 in. Thick, and with the Segal keyway lock cylinders featured in these Mortise lock sets, together with the heavy-duty construction of the internal case and components, you can enjoy the beauty of yesterday's vintage hardware with the strength of modern day security hardware. The knobs of these lock sets are constructed of die-cast and reinforced steel components, and they're finished off with a beautiful wrought, solid, polished brass finish. This lock set includes an 1/8 in. Thick strike plate where both the deadbolt and latch engage into the same rectangular opening, with mounting holes spaced apart at 4-D/8 inches. A Gray plastic dust box is also included for installation beneath the strike plate. As an increased security feature, this lock set features a split spindle knob system designed to prevent breaching of hardware from the exterior side of the door. The spindle half with the female threading and cross pin inserts from the exterior, while the spindle half with the male threading inserts from the interior side of the door. The knobs fasten to the spindle pieces with the set screws found on each knob shaft. Although the handing's of these lock sets are reversible (instructions included), there are matching lock sets available with opposite handed latches ready for installation. Detailed, simple to follow installation instructions are included with each entrance Mortise lock set.