The furlong is a unit of length in the imperial unit system and uses the symbol fur.
One furlong is equal to 1/8 mile, 660 feet, 220 yards, 40 rods, 10 chains or ≈ 201m.
The furlong was a term used to describe the legnth of a furrow in one acre of a ploughed open field (communal field). It now only really remains in the world of horse-racing in UK, Ireland, Canada and the US.
The rod is a unit of length in the imperial and US sytem and uses the symbol rod.
A rod (or perch, pole, lug) is equal to 16.5 feet or 5.5 yards.
It is a building surveyor's tool for measuring distance and is particularly useful as multiples of this unit can make up an exact acre. A perfect acre is a rectangle with edges 660 feet and 66 feet - which is 40 rods by 4 rods; i.e. 1 acre = 160 square rods.