The foot is a unit of length in the imperial unit system and uses the symbol ft.
One foot is exactly equal to 12 inches. It is also exactly equal to 0.3048m. One yard is comprised of three feet.
The foot is just behind the metre in terms of widespread use due to its previous popularity. The US is the only developed country that still uses the foot in preference to the metre.
The UK still uses feet to express human height more than metres.
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.