Metes and bounds

Metes and bounds is a system or method of describing land, real property (in contrast to personal property) or real estate. Newer systems include rectangular (government survey) and lot and block (recorded plat). The system has been used in England for many centuries and is still used there in the definition of general boundaries. The system is also used in the Canadian province of Ontario. By custom, it was applied in the original Thirteen Colonies that became the United States and in many other land jurisdictions based on English common law, including Zimbabwe, South Africa, India and Bangladesh.
Typically the system uses physical features of the local geography, along with directions and distances, to define and describe the boundaries of a parcel of land. The boundaries are described in a running prose style, working around the parcel in sequence, from a point of beginning, returning to the same point; compare with the oral ritual of beating the bounds. It may include references to other adjoining parcels (and their owners), and it, in turn, could also be referred to in later surveys. At the time the description is compiled, it may have been marked on the ground with permanent monuments placed where there were no suitable natural monuments. Surveying has been a subjective process open to interpretation by the person or persons producing the document as well as open discussion to the persons abiding by the document. The variables that originally defined the "bounds" need to be converted to metes by more modern methods. Today the word "art" is being used when discussing surveying as in Surveying is an "Art" leaving much to surveyor opinion to "update" the existing deed. In most areas, urban deeds have defined the boundary lines sufficiently to buy and sell land with sufficient clarity however as one moves further into larger parcels the subjectivity grows. 
Usage.
A typical description for a small parcel of land would be: "Commencing at a corner at the intersection of two stone walls near an apple tree on the north side of Muddy Creek road one mile above the junction of Muddy and Indian Creeks, thence north for 150 rods to the end of the stone wall bordering the road, thence northwest along a line to a large standing rock on the corner of the property now or formerly belonging to John Smith, thence west 150 rods to the corner of a barn near a large oak tree, thence south to Muddy Creek road, thence down the side of the creek road to the point of commencement." The sequence begins with an identified corner serving as benchmark. The description then gives distance, direction and various boundary descriptions as if one were walking the bounds pacing off the distance to the next corner where there is a change of direction. Where watercourses form part of the bounds their meander is generally taken as a straight line between the established corners and their monuments.
In many deeds, the direction is described not by azimuth (a clockwise degree measure out of 360 degrees) but instead by bearing (a direction north or south followed by a degree measure out of 90 degrees and another direction west or east). For example, such a bearing might be listed as "N 42°35' W", which means that the bearing is 42°35' counterclockwise, or west of north. This has the advantage of providing the same degree measure regardless of which direction a particular boundary is being followed; the boundary can be traversed in the opposite direction simply by exchanging N for S and E for W. In other words, "N 42°35' W" describes the same boundary as "S 42°35' E" but is traversed in the opposite direction.
In most distance measures, especially those in older deeds and where measuring distances over a furlong, boundary lengths are listed in rods or poles instead of feet or meters. Rods and poles are equivalent measures equaling 16.5 feet. There are four rods in one chain. English surveyors carried chains (such as a Gunter's chain) with which to measure lengths, as well as poles, and many older legal descriptions of real estate in the United States are given in chains and poles.
Resolving inconsistencies.
Some courts have established a list of priorities to resolve inconsistent descriptions of corners. In descending order starting with the most reliable: (1) natural monuments, (2) artificial monuments such as roads and marked or surveyed lines, (3) adjacent tracts or boundaries, (4) courses or directions, (5) distances, and (6) area or quantity.
Difficulties.
Once such a survey is in place, the corners may have to depend on tradition and long use to establish the line along the boundaries between them. In some areas where land was deeded before 1593, the lengths given predate the changes to the length of the furlong and mile by Queen Elizabeth I. In other places references to the official borders of towns, counties, and states may have changed. Compass directions always have to be tied to a table of annual deflections because magnetic north is constantly changing. The description might refer to "landmarks" such as the "large oak tree" which could die, rot and disappear; or be confused with a different tree that had grown over time. Streams might dry up, meander or change course. Man-made features such as roads, walls, markers or stakes used to mark corners and determine the line of the boundaries between corners may have been moved. As these features move, change and disappear over time, when it comes time to re-establish the corners along the line of these boundaries (for sale, subdivision, or building construction) it can become difficult, even impossible, to determine the original location of the corner. In the metes and bounds system, corners, distance, direction, monuments and bounds are always carried back to the original intent regardless of where they are now. Court cases are sometimes required to settle the matter when it is suspected the corner markers may have been moved.
These kinds of problems caused the United States to largely replace this system except in the east. Beginning with the Land Ordinance of 1785, it began a transition to the Public Land Survey System (PLSS) used in the central and western states. The eastern, or original states, continue to use the metes and bounds surveys of their founders.
History of use in the United States.
This system was imported to the original colonies that formed the United States. It is also used in some states that were previously part of one of the Thirteen Colonies, or where land was allocated before 1785. These include West Virginia, Kentucky, Maine, Tennessee and Vermont. Because Texas was an independent republic prior to statehood, its land system is primarily metes and bounds.
Election constituency boundaries continue to be described by the use of metes and bounds, even in jurisdictions where land plats are not otherwise based upon metes and bounds. Such mapping generally uses streets and their intersections to define the boundaries of election districts, wards, precincts, "inter alia". "E.g.": "From the intersection of Main Street and John Doe Boulevard, thence north to ABC Drive, thence generally east along the median of ABC Drive to 123rd Street, thence..."
Patent law.
In patent law, an application provides background and disclosure necessary to describe an invention, but it is the claims that define the protected aspects. It is therefore said that the claims set out the metes and bounds (see, e.g. in United States patent law, Manual of Patent Examining Procedure § 2173.05(a)) for the protected invention. As a deed might describe a parcel of land, a patent claim carves out systems, methods, etc. that are infringed by something meeting every single one of the claim features. Moreover, an applicant must present an argument for patentability (or, in the United States, an argument against a "prima facie" case of non-patentability) based only on features found within the claims. The requirement to clearly define the metes and bounds of a claim is found in United States patent law at least at 35 U.S.C. 112, second paragraph, which states, "[t]he specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention."