Fence

A fence is a structure used to enclose an outdoor area, forming a boundary. It is typically built with posts connected by boards, wire, rails, or netting. Unlike a wall, a fence lacks a continuous solid foundation along its entire length. An alternative to fencing is a ditch, which may be filled with water to create a moat.

Fences are categorized by function. Agricultural fencing keeps livestock in and predators out. Blast fences redirect high-energy jet engine exhaust for safety. Acoustic fencing, or sound barriers, reduce noise pollution. Crowd control barriers manage movement, while privacy fencing provides seclusion and security. Temporary fencing is used on construction sites for safety and access control. Perimeter fencing prevents trespassing or theft and keeps children and pets from wandering. Decorative fencing enhances property appearance, and boundary fencing marks real property lines. Specialized types include newt, amphibian, drift, or turtle fencing made of plastic sheeting to restrict reptile or amphibian movement, as well as pest-exclusion fences, underground pet fences, pool fences, snow fences, school fences, and solar fences. The Hesco barrier is a modern gabion system for military fortifications and flood control, made of collapsible wire mesh with a heavy-duty geotextile liner. A balustrade or railing prevents falls from edges, common on stairs, landings, balconies, roofs, bridges, cliffs, pits, and near water. Fences also limit intrusion, with support technologies including detectors, peripheral alarm control units, means of deterrence, remote communication systems, and remote alarm receiving units.

By construction, fences vary widely. Brushwood fencing uses wires to compact brushwood. Chain-link fencing is woven wire. Chicane barriers exist. Close boarded fencing uses mortised posts, arris rails, and vertical feather edge boards. Composite fencing blends recycled wood and plastic. Expanding fences or trellises fold on a scissor-like pantograph principle, often as temporary barriers. A ha-ha is a sunken fence. Hedges include cactus fences, hedgerows of living shrubs laid by hedge laying, live woody species fences, and turf mounds in semiarid grasslands. Hurdle fencing uses moveable sections. Pale fencing, or post-and-rail, has vertical posts with tapered ends joined by horizontal rails. Palisades or stakewalls are vertical pales embedded in the ground, often sharpened, with interior walers for reinforcement. Picket fences are waist-high, painted, and partially decorative. Roundpole fences have closely spaced rails, typical of Scandinavia. Slate fences are vertical slate slabs wired together, common in parts of Wales. Split-rail fences are timber laid in zig-zag patterns, used in the United States and Canada. Vaccary fences, from Latin *vaca* for cow, are thin upright stone slabs for restraining cattle in northern UK. Vinyl fencing is also used. Solid fences include dry-stone or rock walls, stockade fences of contiguous round or half-round pointed posts for privacy, and wattle fencing of split branches woven between stakes. Wire fences include smooth wire, barbed wire, electric fences, woven wire (from chicken wire to heavy sheep fence), welded wire mesh, 358 wire fence, double wire fence, 3D wire fence, and roll top fence. Wood-panel fencing uses finished planks in solid panels suspended between posts, creating a wall-like barrier. Wrought iron fencing is also known as ornamental iron.

Legal issues regulate fencing in most developed areas, covering height, material, setback, and aesthetics for commercial, residential, and agricultural zones. Certain facilities are legally required to be fenced for safety and security, including those with open high-voltage equipment (such as transformer stations, often with barbed wire, and mast radiators, which use wooden fences to avoid eddy currents), railway lines (in the United Kingdom), fixed machinery with dangerous moving parts (like amusement park merry-go-rounds), explosive factories and quarry stores, most industrial plants, airfields and airports, military areas, prisons, and construction sites.