The GMS 100 M is a good and well-working unit. The manual should be read. Then place under a wooden plate a screw mark at the top of the plate, the position of the screw and the screw locations using the unit, paying attention to the fine scale. The same with a cable with solid cores, wire is not recognized, but must not be laid under plaster as well. Whoever makes the "dry runs", accumulated enough experience and is not a cable drill.
