Use two clips for panel covers without exposed screws. Loosen sides of panel cover by unscrewing hidden panel screws inside door or clamp type screws. Slip plastic clips between panel cover and panel backbox. Then tighten back the screws so panel cover clamps down on clips. Plastic clip has 1/4 inch truss head screw attached. Clips will be tightly installed with attached screws ready to accept the Panel Lockout. Photo shown has a Panel Lockout with a six inch extension. Use of clips requires adding two inches to the length of the Panel Lockout needed. Clips do not work with panel covers that wrap around back box edge. (We have another product for these types of panel covers. Call us.) The Panel Lockout and extensions are sold separately. Price is per pair of clips. Made in USA