If you are installing a garbage disposal in a kitchen that contains a dishwasher, you will have to run the discharge pipe from the dishwasher into the garbage disposal for everything to work properly. The process is fairly simple, and can be accomplished by most homeowners. One of the more difficult aspects of this project is determining how to create an opening in the garbage disposal to run the discharge line into. Fortunately, the knockout plug makes this an easy process.
Remove the dishwasher drain hose if it is already connected to the garbage disposal.
Press the tip of a screwdriver against the edge of the knockout plug located on the side of the garbage disposal unit.
Tap the end of the screwdriver's handle until the knockout plug breaks free.
Use needle-nose pliers to remove the knockout plug from the inside of the garbage disposal unit so that it does not get caught in the grinding plates.