A magnetic pole detector is a tool used to view and identify the polarity of magnets. Red Team operatives will often choose to use one when searching for the presence of magnetic-based devices such as door contact sensors.
The detector consists of a bar magnet with its north pole painted red and its south pole painted blue. The bar magnet is mounted on a set of gimbals. When held up to the south pole of a magnet, the red end of the indicator will be pointing toward the magnet.