This all-in-one double sided slide rule, used for day and night vessel identification shows aspect for the vessel, (port, stbd, fwd and astern), (60) position of lights and/or (15) day/fog signals, full magnified description for all manner of maritime vessels displayed for each situation. Size 417 x 133 mm. A simple compact but detailed self-tutor. A MUST for every Officer studying for STCW certificates. Identifies all COLREGS Rules 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 34, 35, 36 Displays 60 light configurations Displays 15-day shapes Actual view of vessel for port, starboard, bow and stern lights Visual guide for horn signals Magnifying lens for clear readability of definitions Durable plastic construction