A boundary marker, boundary stone or border stone is a robust physical marker that identifies the start of a land boundary

Border

Borders define geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states and other subnational entities. Some borders—such as a state's internal administrative borders, or inter-state borders within the Schengen Area—are open and...

 or the change in a boundary, especially a change in a direction of a boundary. They have often been used to mark critical points on boundaries between countries

Country

A country is a region legally identified as a distinct entity in political geography. A country may be an independent sovereign state or one that is occupied by another state, as a non-sovereign or formerly sovereign political division, or a geographic region associated with a previously...

 or local administrations but have also been used to mark out the limits of private land-holdings especially in areas where fence

Fence

A fence is a freestanding structure 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 .Fences...

s or wall

Wall

A wall is a usually solid structure that defines and sometimes protects an area. Most commonly, a wall delineates a building and supports its superstructure, separates space in buildings into rooms, or protects or delineates a space in the open air...

s are impractical or unnecessary.

Boundary markers are often made of stone

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 and are typically placed at a notable or especially visible point. Many are inscribed with relevant information such as the abbreviation of the boundary holder and often a date.

Boundary markers may be used to mark property boundaries (land-ownership), or political boundaries.

In developed countries use of markers for land-ownership has in many places been replaced by maps and land ownership registration. Markers are still used extensively for marking international borders; international boundary markers are placed and maintained by mutual agreement of the bordering countries.

See also

• Milestone
  Milestone
  A milestone is one of a series of numbered markers placed along a road or boundary at intervals of one mile or occasionally, parts of a mile. They are typically located at the side of the road or in a median. They are alternatively known as mile markers, mileposts or mile posts...
  
   A milestone or kilometre sign is one of a series of numbered markers placed along a road or boundary at regular intervals, typically at the side of the road or in a median.
• survey marker
  Survey marker
  Survey markers, also called survey marks, and sometimes geodetic marks, are objects placed to mark key survey points on the Earth's surface. They are used in geodetic and land surveying. Informally, such marks are referred to as benchmarks, although strictly speaking the term "benchmark" is...
  
  
• Tripoint
  Tripoint
  A tripoint, or trijunction , is a geographical point at which the borders of three countries or subnational entities meet....
  
  
• Bai Sema
  Bai Sema
  Bai Sema are the boundary stones which designate the sacred area for a phra ubosot within a Thai Buddhist temple .-History:...
  
  which delimit sacred areas