Abstract: A locking device composed of two strips of metal bent into specific configurations to provide a tamper-proof assembly when emplaced on a lidded container. One strip is fixed to the container by a concealed screw within the container. The other strip overlies the lid and includes a portion superposed over a portion of the one strip. The aforesaid portions of the strips are provided with registered holes through which the shackle of a padlock is threaded to lock the assemblage in place and prevent the opening of the lid. The invention is applicable for locking any lidded boxes or containers, e.g. electric meter wiring cabinets, to prevent the tampering with elements within the box such as service wires interposing an electric meter between power lines and house lines.