This highly sensitive tool can detect nails, screws, staples and other metal objects (steel, magnesium, zinc, copper, aluminum, etc.) up to 1" deep (depth depends on the object's size) in wood, plaster, plastics, etc. Ideal for working with salvaged lumber, it scans a swath about 3" wide, allowing material to be checked thoroughly and quickly. A high-pitched tone/LED combination alarm signals detection.