A pile of nails
In woodworking and construction, a nail is a pin-shaped, object of metal (or wood called a treenail) used as a fastener, peg to hang something, or sometimes a decoration. Generally nails have a point on one end and a head on the other. Formerly wrought iron, today's nails are typically made of steel, often dipped or coated to prevent corrosion in harsh conditions or improve adhesion. Ordinary nails for wood are usually of a soft, low-carbon or "mild" steel (about 0.1% carbon, the rest iron and perhaps a trace of silicon or manganese). Nails for concrete are harder, with 0.5-0.75% carbon.
Nails are typically driven into the workpiece by a hammer, a pneumatic nail gun, or a small explosive charge or primer. A nail holds materials together by friction in the axial direction and shear strength laterally. The point of the nail is also sometimes bent over or clinched after driving to prevent falling out.
Nails are made in a great variety of forms for specialized purposes. The most common is a wire nail. Other types of nails include pins, tacks, brads, and spikes.
The history of the nail is divided roughly into three distinct periods:
- the period of the hand-wrought (forged) nail (pre-history until 19th century)
- the period of the cut nail (roughly 1800 to 1914)
- the period of the wire nail (roughly 1860 to the present)
Wrought-iron nails 
To make a wrought-iron nail, iron ore was heated with carbon (to create wrought iron) and shaped into square rods. To make a nail, a blacksmith would heat the rod in a forge, taper the end of the bar while keeping the cross section square. Next, the smith would cut off the taper, and insert it into a nail heading tool with a square hole. The top of the taper would be hammered downward (upset) to create a head.
Nails go back at least to Ancient Egypt — bronze nails found in Egypt have been dated 3400 BC.
The Bible provides a number of references to nails, including the story in Judges of the wife who drives a nail into the temple of her husband while he is asleep, the provision of iron for nails by King David for Solomon's Temple, and of course the crucifixion of Christ.
The Romans made extensive use of nails. One way that we know this is that in the United Kingdom, the Roman army left behind seven tons of nails at the fortress of Inchtuthil in Perthshire.
The term “penny”, as it refers to nails, probably originated in medieval England to describe the price of 100 nails. The letter “d”, which stands for penny, is derived from the Latin name of the Roman coin, the denarius.
Until around 1800, nails were made by hand, and were provided by an artisan known as a nailer or nailor. There were workmen called slitters who cut up iron bars to a suitable size for nailers to work on. From the late 16th century, manual slitters disappeared, with the rise of the slitting mill, which cut bars of iron into rods with an even cross-section, saving much manual effort.
At the time of the American Revolution, England was the largest manufacturer of nails in the world. Nails were expensive and difficult to obtain in the American colonies. Families often had small nail manufacturing setups in their homes; during bad weather and at night, the entire family might work at making nails for their own use and for barter. Thomas Jefferson wrote in a letter, “In our private pursuits it is a great advantage that every honest employment is deemed honorable. I am myself a nail maker.” The growth of the trade in the Thirteen Colonies was theoretically held back by the prohibition of new slitting mills in America by the Iron Act, though there is no evidence that the Act was actually enforced.
The production of wrought iron nails continued well into the 19th century, but ultimately limited to nails for purposes for which the softer cut nails were unsuitable, including horseshoe nails.
Cut nails 
(Rofa Luver) said
From the very beginning, nails were handmade; the nail-making process was slow; and nails were relatively few and expensive. This naturally produced a desire to create machines to speed up and automate the nail-making process.
The slitting mill, introduced to England in 1590, had simplified the production of nail rods, but the real first efforts to mechanise the nail-making process itself occurred between 1790 and 1820, initially in the United States and England, when various machines were invented to automate and speed up the process of making nails from bars of wrought iron. These nails were known as cut nails or square nails because of their roughly rectangular cross section. Cut nails were one of the important factors in the increase in balloon framing beginning in the 1830s and thus the decline of timber framing with wooden joints. Though still used for historical renovations, and for heavy-duty applications, such as attaching boards to masonry walls, cut nails are much less common today than wire nails.
The cut-nail process was patented in America by Jacob Perkins in 1795 and in England by Joseph Dyer, who set up machinery in Birmingham, cutting nails from sheets of iron, making sure that the fibres of the iron ran down the nails. The Birmingham industry expanded in the following decades, but reached its greatest extent in the 1860s, after which it declined due to competition from wire nails, but the Birmingham industry survived until the outbreak of World War I.
Wire nails 
Wire nails were also known as "French nails" for their country of origin. Belgian wire nails were beginning to compete in England in 1863. Joseph Henry Nettlefold was making wire nails at Smethwick by 1875. Over a following decades, the nail-making process was almost completely automated. Eventually the industry had machines capable of quickly producing huge numbers of inexpensive nails with little or no human intervention.
With the introduction of cheap wire nails, the use of wrought iron for nail making quickly declined, as more slowly did the production of cut nails. In the United States, in 1892 more steel-wire nails were produced than cut nails. In 1913, 90% of manufactured nails were wire nails. Nails went from being rare and precious to being a cheap mass-produced commodity.
Types of nail include:
- floor brad (aka 'stigs') - flat, tapered and angular, for use in fixing floor boards
- oval brad - Ovals utilize the principles of fracture mechanics to allow nailing without splitting. Highly anisotropic materials like regular wood (as opposed to wood composites) can easily be wedged apart. Use of an oval perpendicular to the wood's grain cuts the wood fibers rather than wedges tham apart, and thus allows fastening without splitting, even close to edges.
- brass tack - Brass Tacks are commonly used where corrosion may be an issue, such as furniture where contact with human skin salts will cause corrosion on steel nails.
- bullet head nail
- canoe tack
- carpet tack
- casing - Casing nails have a head that is smoothly tapered, in comparison to the "stepped" head of a finish nail. When used to install casing around windows or doors, they allow the wood to be pried off later with minimal damage when repairs are needed, and without the need to dent the face of the casing in order to grab and extract the nail. Once the casing has been removed, the nails can be extracted from the inner frame with any of the usual nail pullers.
- coffin nail
- coil nail
- fiber cement
- finish - has the same diameter as a box nail.
- joist hanger
- masonry - fluted nail for use in concrete
- nail bomb shrapnel
- panel pin
- plastic strip
- gutter spike
- ring shank - nails that contain ridges along the shank to provide extra support, an example would be the HurriQuake
- roofing tack
- shake - small headed nails to use for nailing sidewall shakes
- Teco - 1-1/2 x .148 shanks nails used in metal connectors (usually hurricane ties)
- veneer pin
- wire-weld collated
Most countries, except the United States, use a metric system for describing nail sizes. A 50 x 3.0 indicates a nail 50 mm long (not including the head) and 3 mm in diameter. Lengths are rounded to the nearest millimetre.
For example, finishing nail* sizes typically available from German suppliers are:
- Drahtstift mit Senkkopf (Stahl, DIN 1151)
United States penny sizes 
In the United States, the length of a nail is designated by its penny size, written with a number and the abbreviation d for penny; for example, 10d for a ten-penny nail. A larger number indicates a longer nail, shown in the table below. Nails under 1¼ inch, often called brads, are sold mostly in small packages with only a length designation or with length and wire gauge designations; for example, 1" 18 ga or 3/4" 16 ga.
Penny sizes originally referred to the price for a hundred nails in England in the 15th century: the larger the nail, the higher the cost per hundred. The system remained in use in England into the 20th century, but is obsolete there today. The d is an abbreviation for denarius, a Roman coin similar to a penny; this was the abbreviation for a penny in the UK before decimalisation.
- Box — a wire nail with a head; box nails have a smaller shank than common nails of the same size
- Bright — no surface coating; not recommended for weather exposure or acidic or treated lumber
- Casing — a wire nail with a slightly larger head than finish nails; often used for flooring
- CC or Coated — "cement coated"; nail coated with adhesive (cement) for greater holding power; also resin- or vinyl-coated; coating melts from friction when driven to help lubricate then adheres when cool; color varies by manufacturer (tan, pink, are common)
- Common — a common construction wire nail with a disk-shaped head that is typically 3 to 4 times the diameter of the shank: common nails have larger shanks than box nails of the same size
- Duplex — a common nail with a second head, allowing for easy extraction; often used for temporary work, such as concrete forms or wood scaffolding; sometimes called a "scaffold nail"
- Drywall — a specialty blued-steel nail with a thin broad head used to fasten gypsum wallboard to wooden framing members
- Finish — a wire nail that has a head only slightly larger than the shank; can be easily concealed by countersinking the nail slightly below the finished surface with a nail-set and filling the resulting void with a filler (putty, spackle, caulk, etc.)
- Galvanized — treated for resistance to corrosion and/or weather exposure
- Electrogalvanized — provides a smooth finish with some corrosion resistance
- Hot-dip galvanized — provides a rough finish that deposits more zinc than other methods, resulting in very high corrosion resistance that is suitable for some acidic and treated lumber;
- Mechanically galvanized — deposits more zinc than electrogalvanizing for increased corrosion resistance
- Head — round flat metal piece formed at the top of the nail; for increased holding power
- Helix — the nail has a square shank that has been twisted, making it very difficult to pull out; often used in decking so they are usually galvanized; sometimes called decking nails
- Length — distance from the bottom of the head to the point of a nail
- Phosphate-coated — a dark grey to black finish providing a surface that binds well with paint and joint compound and minimal corrosion resistance
- Point — sharpened end opposite the "head" for greater ease in driving
- Pole Barn — long shank (2 1/2in to 8in, 6 cm to 20 cm), ring shank (see below), hardened nails; usually oil quenched or galvanized (see above); commonly used in the construction of wood framed, metal buildings (pole barns)
- Ring Shank — small directional rings on the shank to prevent the nail from working back out once driven in; common in drywall, flooring, and pole barn nails
- Shank — the body the length of the nail between the head and the point; may be smooth, or may have rings or spirals for greater holding power
- Sinker — these are the most common nails used in framing today; same thin diameter as a box nail; cement coated (see above); the bottom of the head is tapered like a wedge or funnel and the top of the head is grid embossed to keep the hammer strike from sliding off
- Spike — a large nail; usually over 4 in (100 mm) long
Nails in art 
Before the 1850′s bocce and petanque boules were wooden balls, sometimes partially reinforced with hand-forged nails. When cheap, plentiful machine-made nails became available, manufacturers began to produce the boule cloutée — a wooden core studded with nails to create an all-metal surface. Nails of different metals and colors (steel, brass and copper) were used to create a wide variety of designs and patterns. Some of the old boules cloutées are genuine works of art and valued collectors items.
See also 
- Oxford English Dictionary Second Edition on CD-ROM (v. 4.0) © Oxford University Press 2009. Nail II. 4. a.
- Bible, 1 Chronicles 22:3.
- Kirby, Richard Shelton. Engineering in history. 1956. Reprint. New York: Dover Publications, 1990. 325. ISBN 0486264122
- G. Sjögren, 'The rise and decline of the Birmingham cut-nail trade, c. 1811-1914', Midland History 38(1) (2013), 36-57.
- Notes on building construction arranged to meet the requirements of the syllabus of the Science & Art Department of the Committee of Council on Education, South Kensington. Eds 1-8. ed. London: Rivingtons, 1875,1915. 441.
- G. Sjögren, 54-5.
- "A New English Nail Machine". Hardware. 7 Feb 1890. Retrieved 19 April 2013.
- "Penny" (subscription required). Oxford English Dictionary (2nd ed.). Retrieved 2010-05-30. "Applied to nails, such adjectives denote the original price (in 15th c.) per hundred; as fivepenny nail, a nail which cost 5d. a hundred, tenpenny nail, a nail costing 10d. a hundred. (These names persisted after the prices fell, as they began to do in some places before 1500, and they were eventually used to designate sizes of nails.)"
- H. Littlehales (1905). Medieval Rec. London City ChurchCited in the Oxford English Dictionary under "Penny" with a quote from 1426-1427.
- "Penny". sizes.com. Retrieved 2010-01-10.
- Norman Scott Brien Gras (1918). The Early English Customs System. Harvard University Press, Cambridge (MA). p. 701. Cited at sizes.com with a quote from 1507.
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