The mortise is the cut out material on the end of the door stile shown below. Because these hinges are wider than the 1 1/8″ thick door the mortise will go from front to back completely as shown below. The mortise allows the hinge to fit flush with the door stile to make the door sit equal distance from both sides. Essentially making the door centered. Sometimes this is not the case and mortising is not necessary. The hinge is 1/8″ thick and the mortise allows the hinge to be flush. We do not recommend installing the hinge on the face of the door.
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