The unique Target Identification System (TID)™ is designed to save time from digging unnecessary holes, especially in hard or frozen ground. Great for Utilities, Water Work Municipalities, and Construction Road departments to locate manhole covers, catch basins, cast iron pipes, septic tank handles, oil tanks, steel drums, well casings and more. The 2100 can effectively locate valves and curbs up to 9 ft deep, survey markers up to 8 ft deep, and PK nails up to 14'' deep. Can distinguish between a manhole cover and a close iron valve.