Set another gage to one half the thickness of the knuckle and gage on the door face the depth of the gains.

Chisel out the gains, set the hinges in place, bore the holes, and drive the screws.

Place the door in position again to test the fit.

If all is well, mark the position of the hinges on the frame, gage and cut the gains, and fasten in the hinges.

Where the hinge is gained its full thickness into the door, no gain, of course, is cut in the frame.