Browse edge protectors designed to prevent scratches and injuries. Huge Catalog! Over 45,000 products in stock. STURDY STEEL CONSTRUCTION: These electric boxes cover with 1 /2” knockouts are a perfect fit for 4-inch square boxes, help in optimizing electrical setups and offer protection from accidental electrocution. PREMIUM MATERIALS: Constructed using top galvanized steel, electric outlet cover is. Slip-on Design with 3M Adhesive for a Secure fit. Choose from rubber trims, metal corners, and flexible guards for any project. They are one-pole modular units with an interlocking dovetail feature that enables ganging of the blocks to create multi-pole configurations according to application requirements.