Rod
A rod is a unit of length, equal to 11 cubits, 5.0292 metres or 16.5 feet. A rod is the same length as a perch and a pole. The lengths of the perch (one rod) and chain (four rods) were standardized in 1607 by Edmund Gunter.
The length is equal to the standardized length of the ox goad used by medieval English ploughmen; fields were measured in acres which were one chain (four rods) by one furlong (ten chains). An acre is 160 square rods.