I hated the black hole that appeared when I installed corner bifold doors in my kitchen cabinets. To get rid of this annoying gap, I decided to make the main door (the one with the hinges) 3/4-in. wider, so it would extend behind the second door. This alteration required cutting a pair of 3/4-in.-deep notches in the main door in order for the hinges to work properly (these notches are only visible when the doors are open). I also had to measure from the inside edge of each notch to drill the bifold hinge cup holes.