How to Install a Vent Behind an Overmounted Microwave Oven

Push a duct transition piece over the microwave's exhaust adaptor, located on the back.

Wrap duct tape around the bottom of the duct transition piece, where it meets with the exhaust adaptor. Wrap it around the entire circumference of the duct piece to seal it closed.

Tape the wall template -- included with the microwave -- on the wall where the microwave will hang. The template should identify where the brackets of the microwave should sit, as well as where the ventilation pieces should go through the wall.

Cut through the template along the lines shown on the template. Push a drywall saw or a utility knife into the template and through the wall just until it breaks through the wallboard. Move the saw in and out slowly along the ventilation lines on the template. If using a utility knife, pull the knife along the ventilation lines.

Push additional duct pieces over the transition piece. The specific configuration will vary. The pieces must run from the transition piece out to the exterior vent. Use as many straight and elbow pieces as necessary to connect to the vent, but ideally, limit the number of elbows to one to prevent blockages.

Wrap duct tape around each section to seal them.