Coppices provided wood for many purposes, especially charcoal before coal was economically significant in metal smelting. A minority of these woods are still operated for coppice today, often by conservation organisations, producing material for hurdle-making, thatching spars, local charcoal-burning or other crafts. The only remaining large-scale commercial coppice crop in England is sweet chestnut which is grown in parts of Sussex and Kent. Much of this was established as plantations in the 19th century for hop-pole production (hop-poles are used to support the hop plant while growing hops) and is nowadays cut on a 12 to 18-year cycle for splitting and binding into cleft chestnut paling fence, or on a 20- to 35-year cycle for cleft post-and-rail fencing, or for sawing into small lengths to be finger-jointed for architectural use. Other material goes to make farm fencing and to be chipped for modern wood-fired heating systems.