Garbage Disposal Knockout Plug

Each knockout plug is typically stamped from the same type of material as the tube or hole it blocks.

Garbage disposal knockout plug.

When knockout plug falls into disposer you may remove it or simply grind it up when the disposer is used. The plug is similar to the knockout plug on a metal electrical box and you remove it the same way. Before long the plug will fall back into the disposal unit. Using the hammer lightly tap the back of the screwdriver against the knockout plug repeatedly.

As later in the same guide it provides these pearls of wisdom. Your disposer is ruggedly built to give you many years of trouble free service. Insert a screwdriver into the drain opening far enough to contact the plug then tap the screwdriver firmly with a hammer to knock out the plug. Move the screwdriver around the perimeter of the plug tapping all the while with the hammer so you can cleanly remove the whole knockout plug.

One common use for a knockout plug is the dishwasher connection found on many garbage disposals.