How to Install Under Counter Microwave in Existing Cabinet

Remove the existing door to the cabinet where the microwave will be installed by loosening each of the screws attached to the hinge on the door and on the cabinet itself. Remove the contents of the cabinet. Sand down any exposed rough edges caused by the hinge.

Measure the vertical distance required by the microwave within the cabinet so you'll know where to install the microwave shelf. Add 1 inch to the measurement and mark that distance within the cabinet, measuring from the ceiling of the cabinet down and marking it on both side boards of the cabinet.

Remove any shelves that will be in the way of the new microwave or that will be useless once the microwave shelf is installed. Use the drill to loosen any screws and remove any pegs that were holding these shelves in place so they don't interfere with the microwave's position.

Position the shelf for the microwave right on the line you marked, so that the top surface of the shelf board is even with the marking for microwave clearance. Hold the shelf in position and drill three evenly spaced holes through the sides of the cabinet and into the shelf board. Thread 2-inch wood screws through washers and into these holes and tighten them with the drill.

Slide the microwave onto the shelf and ensure that it opens and closes appropriately. Determine the best location for the cord to exit the cabinet and drill a hole to accommodate the cord so it can be plugged in elsewhere.