Refined by Les Schatten especially for guitar shops, the Schatten Magnet Polarity r is useful for troubleshooting and testing pickups and wiring.
Pickup rewinding specialist J.M. Rolph has noted, "How many times have you wired a pickup and found it's magnetically out of phase, with the same thin, low-powered sound as a pickup that's wired out of phase, even though the lead wires looked right?" By indicating the north or south magnetic orientation of a pickup's polepieces, this polarity r can help you avoid the problem.
With a basic knowledge of vintage pickup magnet polarities (instructions are included), this tool is also a quick way to determine a pickup's authenticity.
If you do a lot of work on guitar pickups and amp electronics, you'll want this simple and effective tool in your toolbox.