The door hinges for a wooden door need to be recessed into both the edge of the door and the door jamb. If the hinges are not recessed into a mortise, the gap on the hinge side of the door will be larger than necessary. While the mortise can be cut by hand with a hammer and chisel, a cleaner and more consistent method is to route the door hinge's mortises with a router and a hinge mortise jig.
Place the door on its side with the edge to receive the hinges facing upwards, and the side of the door on which the hinge pin will reside on the opposite side from your body.
Position the hinge mortise jig over the location where one of the door hinge mortises will be cut. Clamp the jig into place with a quick-action woodworking clamp.
Insert a 1/2-inch straight-cutting bit into a router with a guide collar installed. The tip of the bit should be adjusted so that its depth of cut is the thickness of the jig plus the thickness of the hinge.
Grasp the router firmly and turn it on. Place the router with the guide collar inside the jig, and route out the entire mortise on the side of the door. Lift the router out of the jig and turn off the router.
Move the jig to the other hinge locations on the door and then on the jamb, and repeat step 4 to route out the other mortises.
Place a chisel along the edge of the mortise in each rounded corner, and scribe out the square corner. Then lift out the corner with the edge of the chisel. If your hinges have rounded corners, you can skip this step.
Place the hinge in the mortise, and attach the hinge to the door with the supplied Phillips-head screws.