Maille was the earliest form of metal armour and was probably invented before the 5th century by the ancient Celts. The name mail comes from the French word "maille" which is derived from the Latin "macula" meaning "mesh of a net". The armour itself involved the linking of iron or steel rings, the ends of which were either pressed together, welded or riveted. Sometimes the rings were stamped out of a sheet of iron and these were then used in alternate rows with riveted links. The most common form of Maille is the "four-in-one" pattern in which each link has four others linked through it. A few shirts have been found that appear to have been made of quilted fabric or leather to which were sewn rings and scales, and these shirts are not considered "true" mail.

Each piece of mail was fashioned specifically for whichever part of the body it was intended to protect. For the head there were the coif, aventail, mail fringe and a "bishop's mantle"; for the torso, the shirt, hauberk, skirt and breeches; for the upper limbs, mail sleeves and mittens; for the lower limbs, chausses and sabatons.

Until the 14th century, mail was the primary armour for the average soldier. The main use of Maille was to stop the wearer from being cut by the opponents blade. Mail did nothing to stop the damage from the force of the blow however, and was usually worn over a thick, padded undergarment. From the 1320's, shirts of mail, known as hauberks or byrnies, were often provided with flared sleeves covering to the middle of the forearms, and were long enough to reach past the wearer's knees. Some of the larger hauberks often had sleeves that were extended to form mittens for the hands. This was also the period when a shorter type of hauberk, the haubergeon, began to be used more regularly, its lower edge stopping to just above the knees. Some haubergeons had a flap-like extension at the center of the rear edge of the base which could be pulled up between the legs and laced in front to form a breke of mail to protect the genitals.

As there were developments in the armouring world, mail began to have a subordinate role in relation to plate armour, first being used as a linking elements for the various plates and then, in the 15th century, it was used to protect the more vulnerable parts of the body such as the elbow, neck, and knees joints. Mail shirts retained defensive importance during the 16th century with light horse and infantry armours, especially in conjunction with small pauldrons or spaulders and elbow length gauntlets which left part of the arms bare. In these cases, sleeves of mail were attached to the arming doublet worn under the armour. After this time, the use of mail slowly diminished as better plate armour was developed for the arms and legs, although it was still in use as late as the 17th century in Eastern Europe and the Middle East. The craft of making mail is quite separate and distinct from that of the process of manufacturing plate armour. Because so much mail was produced, we can assume the method of manufacture must have been fast, allowing for division of the labour within the workshop. The most skilled task, the final linking of the rings, would have been done by the master craftsman, who would have been kept supplied with rings and rivets. The early stages in the production of mail, (the simple, labour intensive tasks) were left to apprentices and assistants.

There were two possible methods of producing the rings for the mail. Closed rings were made by punching them from a sheet of metal with a double punch, or by simply punching a hole in a piece of metal and trimming the outside edge. Open rings were usually made from iron wire. There has been (and still is) much controversy as to whether or not the ancient armourer knew the art of wire-drawing. This process of making wire involves the drawing of a forged metal rod through successively smaller and smaller holes until the rod was the right size for making rings. A similar method was to cut the wires from a thin metal sheet and then file, scrape and hammer them into the right size. It is more likely that a combination of both of these methods was used in which a strip of metal was cut from a sheet about 3 mm thick and then this was drawn through smaller and smaller holes, until the proper diameter of wire was reached. This length of wire was then wrapped around a rod the diameter of the required ring, using a device called a mandrill, to form a long coil. The coil was then cut up one side from end to end, producing a number of metal rings.

In all the methods described so far the metal was worked cold, but as soon as it became hard through working, it had to be annealed (heated until it was softened). This was done by bringing the rings to a red heat in the forge and then leaving them to cool. For overlapping the rings, they would be driven through a tapering hole in a steel block with a punch. After this overlapping, the rings would then be annealed once more. The next stage was the flattening of the ends, done by hammering. These flattened, overlapped ends were then punched or bored to make a hole for the rivet. Rivets were always made of iron, even if the rings were of brass. Rivets were made of wire with one end being hammered flat and the other cut to a point with wire cutters.

The last stage, the linking, was now done by the master craftsman. The most common pattern, as mentioned earlier, was the four-in-one pattern, in which each ring has four others linked through it. The rivets were burred over by the master using a hammer. When the mailmaker used closed rings he arranged them in alternated rows with open rings. The closing of the rings was sometime done by hammer welding.

While assembling the rings, the mailmaker must have used a pattern resembling a modern knitting pattern. Sadly, none of these patterns have survived, but it is known that garments of mail were shaped by adding or leaving out rings in each row. Occasionally, for a stronger shirt, two rings were used in the place of one in ordinary mail; or sometime the garment was rolled up in charcoal and case-hardened. Some rings bear the maker's marks, an example being a mail shirt in the Tower of London, into which is woven three brass rings. The first ring is marked with the amourer's name (bertolt parte), and the second the name of his town (isrenloen), the third is plain.