‘X’ consists of a rectangular wooden card about 2 by 1 inches (5.1 cm × 2.5 cm), to which a string with several equally spaced knots is attached through a hole in the middle of the card. The ‘X’ is used by placing one end of the string in the teeth while the other end is held away from the body roughly parallel to the ground. The card is then moved along the string, positioned so the lower edge is even with the horizon, and the upper edge is occluding a target star, typically Polaris because its angle to the horizon does not change with longitude or time. The angle can then be measured by counting the number of knots from the teeth to the card, or a particular knot can be tied into the string if traveling to a known latitude. ’x’ is an Arabic navigation tool while ‘x’ in Tamilnadu is a sensation. Identify ‘x’
