The link, sometimes called a Gunter’s link, is a unit of length formerly used in many English-speaking countries. A link is exactly 66/100 of a foot, or exactly 7.92 inches.
The unit is based on Gunter's chain, a metal chain 66 feet long with 100 links, that was formerly used in land surveying. Even after the original tool was replaced by later instruments of higher precision, the unit itself was commonly used in this application throughout the English-speaking world (e.g. in the United States customary system of measurements and the Imperial system). The length of the foot, and hence the link, varied slightly from place to place and time to time, but in modern times the difference between, say, the US survey foot and the international foot is two parts per million. The link fell out of general use in the 20th century.
This article uses material from the Wikipedia article "Link (unit)", which is released under the Creative Commons Attribution-Share-Alike License 3.0.