After the doors are fitted into the cabinet opening the next step is to layout and create the hinge mortises for the knife hinge pairs. Each door has one pair of knife hinges as they come in pairs. I use spacers and my small adjustable square to make certain the doors are spaced uniformly from the cabinet case. This is important as the door reveal all around needs to be uniform. After the hinges mortises are marked the process of creating the recesses is accomplished with a set of sharp chisels and a small mallet.
Once the hinges mortises have been created on the doors, the hinge markings are transferred from the doors to the cabinet to maintain accuracy.I do this with the use of a spacer. The spacer allows me to maintain the same reveal of the door from the cabinet sides. Creating the hinge mortises with hand tools is somewhat of a pleasant task although it can take a while. Care needs to be exercised with grain orientation as the grain is reversed depending on which corner of the cabinet is being mortised. I use both chisel bevel down and back down orientation to remove waste from the hinge.
The outline of the hinge and its offset from the edge of the cabinet and doors is fairly important, I usually mark this with a sharp knife, then with a wide chisel define the mortise using these fine knife markings. Once this is accomplished, removing material from the recess is fairly foolproof. I remove wood from the hinge recess in stages, exercising care not to go too deep in one pass of the chisel. To the left, a photo of the completed knife hinge mortise on a door, one of four to be completed.