The bottom side of the top cabinet will need several holes drilled into it. A template, included with the microwave installation instructions, is taped to the underside of the top cabinet. Drill holes for support screws, the power cord and the exhaust adapter as shown on the template.
If your top cabinet is made of metal, use a nylon grommet around the power cord hole to prevent the power cord from being cut by the sharp metal edge of the drilled hole.
If the front of the cabinet hangs below the bottom of the cabinet, filler blocks should be used to avoid the over-tightening of the support screws. Over-tightening will severely damage the microwave's casing.