If you have ever been on the water at night and wondered if the marine navigation lights you see are from an approaching or fleeing vessel, or if the vessel is a fishing trawler or super tanker, then LIGHTrule is for you. This simple-to-use vessel identification tool is inexpensive security for night travel and should be an essential part of the equipment found on any boat. LIGHTrule is also an excellent aide for navigation classes and Coast Guard exams. - Identifies all COLREGS- Displays 60 light configurations- Displays 15 day shapes- Actual view of vessel for port, starboard, bow & stern lights- Visual guide for horn signals- Magnifying lens for clear readability of definitions- Durable plastic construction- Lifetime warranty