Monday Answer
Dan was correct. The item was a �KAMAL�. It is used to determine latitude. It is an astoundingly simple device honed by experience to provide real information based on generations of travelers. It is used by attaching a wooden rectangle by a string of fixed length or with fixed knots in the string and held by the teeth and then stretched to arms length. The wood can vary from one to six inches high (depending on the pre determined location of the desired end port). Up to 20 degrees and 3� x 1 � board will work. Above 20 degrees to 40 degrees a 6� x 3 1/2� board is needed.
First find the North Star. Then holding the rectangular piece of wood with the bottom dead on the horizon and one of the top corners aimed at the star. If the North Star appears above top left or right corner the sought after latitude is to the South. If it is below the corner the desired latitude is north. If the corner is at the North Star, you are on the right latitude.
For the Arabs the North Star was available. But depending on the latitude of the desired port the wooden card would have been different heights.
The accuracy of the Kamal was about thirty miles which was easily corrected for after traveling the distances of the Mediterranean or Indian Oceans. The operation of the Kamal was easiest if you �had been there and done that�. For that reason, the size of the boards and the knotting of the string often had a master unit by which others could be made. Family�s guarded their secrets but eventually clans were included and then the �secret� became available to a wider group of occupations.
A kamal is still used by sea kayakers for various measurements. If you calibrate it, you can use it to find distance offshore from a land mass of known length. If a chronometer is available to find the time of Local Apparent Noon, longitude can be determined. Even Boy Scouts learn that a similar device can double as a sun compass.
Most any browser can provide information. Two other sources� Quest for the Past�, page 216. Latitude Hooks and Azimuth Rings, Dennis Fisher, p20.