Security marker pens or UV Markers with fluorescent ink that glows when illuminated with a UV light is often used to invisibly mark valuable household items in case of burglary. There are especially security maker pens formulated for writing on non-porous surfaces such as glass, plastics, metals, etc. The inks that have been applied and can then be identified by using a black light or other UV light source. Security marker pens can be obtained commercially and are widely used as a crime countermeasure.