Recessed box made of special steel (Magnelis) for mounting of VD 500 in floors, walls or other hard surfaces. It is designed for mounting and cast into the floor or on the walls of the museums, vaults, safe deposits, gold deposits, value depots and other high risk objects. The box has threaded holes for VD 500. The box is attached with supplied expansion bolts that provides a large detection range but also to level the box during assembly so that it fits in level with the floor or wall during installation. For mounting in the floor or wall, VD 503 has a box in Magnelis steel instead of a polystyrene block like VD 502 and can be mounted against a mold before casting the wall or floor. With an M8 threaded rod, wing nut and washer, the box is locked against the mold. After casting when the mold is to be removed, loosen the wing nut and then loosen the casting box from the mold and remove the mounting pliers. It can also be mounted in a hollowed-out hole in the wall or floor, and by using the supplied expander bolts it can be leveled in the same height against the surface. Then fill the hole around the box with concrete. There are ready made “knock out holes” for electrical pipes for the wiring, which makes installation easier. The box has also opening contact to provide extra security. It also includes a lid in anodized aluminum for wall mounting that is slightly larger in size than the size of the box to be able to cover any irregularities.