Very few walls are ever plumb. Even walls framed with engineered studs have bumps and dips
at drywall seams. Sometimes cabinets aren't perfect either. The side panels may be slightly
out of square with the face frame, or a backing panel may not be flat across the rear.
Imperfections in walls and cabinets make aligning the faces of cabinet runs difficult;
particularly when cabinets are installed one cabinet at a time. These problems can be
overcome by ganging cabinets together before mounting them to the wall. This approach
is faster and more precise than mounting cabinets individually.
Cabinets can be preassmbled on the floor resting upright or on their backs. Gang a run of cabinets together by screwing the face-frames of the adjoining cabinets together. Clamp a straight piece of wood (or a level) the length of the run of cabinets onto the front of the face-frames before screwing them together. Screws joining the rear of the cabinets can be driven through the top of the cabinet side panels where they will never be seen. Shims should be used between the top rear of each cabinet. Use three screws on cabinets taller than 24" and two screws on ones shorter. Locate screws where they are least likely to be seen such as behind the hinges. Once the front and top of the cabinets are joined they will stay together as a single unit. This method will give perfectly aligned cabinets prior to installation.
Installing crown moulding is a snap on cabinets when they are a single unit sitting on the floor instead of screwed to the wall. This is the easiest way to do it: Lift the assembled cabinets to the proper height for the crown moulding using the E-Z Lift Cabinet Jack and mark the bottom of the crown on each end of the bank of cabinets. Then lower the cabinets, screw blocking to the top rails, and install the crown by screwing through the blocking and into the crown from behind. With this technique there are no nail holes to be filled. With the assembled cabinets still on the lift raise the cabinets so the crown moulding is against the ceiling and screw the cabinets to the wall.