The Bridgeport Bridgeport 1691 1/2" Steel Knockout Hole Plug for Indoor and Outdoor caps unused knockout holes in a box or enclosure. Electrical codes require that unused knockout holes be sealed to prevent outside tampering, electrocution, and electrical fires. Operators can quickly and easily cap unused knockout holes with the steel knockout plug. This steel plug can be used in both indoor and outdoor applications. The steel body ensures reliable performance. Our knockout plugs are engineered with the quality and innovation that allows contractors to save time and money on every job. When you need quality electrical fittings for more efficient jobs, look for Bridgeport Orange.