4-Hole Corner Gusset - Electro-Galvanized allow for connections at the corners of your strut channel frame that sit flush to the top of two channel lips meeting at a 90 degree angle. Gussets have greater surface area than traditional corner flat fittings. The corner plates use 9/16" punched holes. Electro-Galvanized Steel should be used in interior applications where conditions are dry, and humidity is low.