A fence is a freestanding linear structure consisting of a mesh, series of posts, wire grid, metal sheet, or other flat structure requiring internal reinforcement, which is designed to restrict or prevent movement across a boundary. It is generally distinguished from a wall by the lightness of its construction: a wall is usually restricted to such barriers made from solid brick or concrete, blocking vision as well as passage.

The barrier follows a boundary and restricts crossing through its mesh, posts, or sheeting. It need not block the view through it.

The lighter construction generally distinguishes a fence from a solid wall. An opaque metal sheet can still form a fence, so visibility alone is not decisive.