What measurement is a link?

A "link" is a measure of length: 7.92 inches. Here's how that number arose. The primary tool used by surveyors in North America from the 1600s through the end of the 1800s was a "Gunter's chain," measuring 66 feet long, usually with 100 swiveled links. In that system, a "link" was a measure of length that consisted of one of the standardized links in the chain: 7.92 inches.