Weft-knit fabrics can be divided into two types: those that have selvages (side edges) and those that are tubes, where the side edges have been joined. The former are knit using "flat knitting", whereas the latter are knit using "circular knitting", also known as "knitting in the round".
In flat knitting, the hand-knitter generally knits from right-to-left on one side of the fabric, turns the work (over), and then knits right-to-left back to the starting position. Usually one side of the fabric is considered the right side, the one that faces outwards for viewing; the side that faces inwards, towards the body, is known as the wrong side. Thus, flat knitting involves knitting one row on the right side, then one row on the wrong side, etc. Stitches knit on the wrong side are reversed in appearance; for example, a knit stitch carried out on the wrong side will appear as a purl stitch on the right side, and vice versa. Thus, the uniform stockinette fabric requires that the hand-knitter knit all the stitches on the right side, and purl all the stitches on the wrong side. For comparison, garter-stitch fabric is produced if the knitter knits (or purls) every stitch in every row, regardless of which side is being worked.
In circular knitting, the knitter generally knits everything from one side, usually the right side. Circular knitting is usually carried out on a single circular needle, although this becomes more difficult as the radius of the tube gradually shrinks. In such cases, the knitter can resort to a variety of alternative techniques, such as double-pointed needles, knitting on two circular needles, a Möbius strip-like "magic needle" approach, or careful use of slip-stitch knitting or equivalently double knitting to knit the back and front of the tube.
Most Western-style knitters follow either the English style (in which the yarn is held in the right hand) or the Continental style (in which the yarn is held in the left hand). A third but less common method, called combination knitting, may also be used.
Once the knitted piece is finished, the remaining live stitches are "cast off." Casting (or "binding") off loops the stitches across each other so they can be removed from the needle without unravelling the item. Although the mechanics are different from casting on, there is a similar variety of methods.
In knitting certain articles of clothing, especially larger ones like sweaters, the final knitted garment will be made of several knitted pieces, with individual sections of the garment knit separately and then sewn together. Seamless knitting, where a whole garment is knit as a single piece, is also possible. Elizabeth Zimmermann is probably the best-known proponent of seamless or circular knitting techniques. Smaller items, such as socks and hats, are usually knit in one piece on double-pointed needles or circular needles. (See Circular knitting.)
One of the earliest known examples of knitting was finely decorated cotton socks found in Egypt in the end of the first millennium AD. The first knitting trade guild was started in Paris in 1527. With the invention of the knitting machine, however, knitting "by hand" became a useful but non-essential craft. Similar to quilting, spinning, and needlepoint, knitting became a social activity.
Hand-knitting has gone into and out of fashion many times in the last two centuries, and at the turn of the 21st century it is enjoying a revival. According to the industry group Craft Yarn Council of America, the number of women knitters in the United States age 25–35 increased 150% in the two years between 2002 and 2004. While some may say knitting has never really gone away, this latest reincarnation is less about the make do and mend of the 1940’s and 50’s and more about making a statement about individuality as well as developing an innate sense of community. Additionally, many contemporary knitters have an interest in blogging about their knitting, patterns, and techniques.
There are now numerous groups that are not only growing individually, but also forming international communities. Communities also exist online, with blogs being very popular, alongside online groups and social networking through mediums such as Yahoo! Groups, where people can share tips and techniques, run competitions, and share their patterns. More people are finding knitting a recreation and enjoying the hobby with their family. Knitting parties also are becoming popular in small and large communities around the U.S. and Canada.
The oral histories of many knitters have been collected, and suggest that hand-knitting is often associated with compassion. "I knit love into every stitch" is a common refrain.
Knitting especially large or fine garments such as sweaters can require months of work and, as gifts, may have a strong emotional aspect. The so-called sweater curse expresses the experience that a significant other will break up with the knitter immediately after receiving a costly hand-knit gift such as a sweater. A significant minority of knitters claim to have experienced the sweater curse; a recent poll indicated that 15% of active knitters say they have experienced the sweater curse firsthand, and 41% consider it a possibility that should be taken seriously. Although sometimes labeled a "superstition", the sweater curse is not treated in knitting literature as anything paranormal.
Hand-knitting is generally relaxing and repetitive, Some practitioners have noted that these factors, combined with its compassionate nature, make hand-knitting well-suited for meditational or spiritual practice.
Knitting is sometimes featured in literature. Knitting and its techniques may be used as a metaphor; its meditative and spiritual aspects may be emphasized; it may signal various types of domesticity; or it may be used for dramatic irony, as when an apparently harmless knitter proves deadly and implacable. Examples from 19th century novels include Madame Thérèse Defarge in Charles Dickens' A Tale of Two Cities, Anna Makarovna in Leo Tolstoy's War and Peace, various characters in Jane Austen's novels and Miss Ophelia in Harriet Beecher Stowe's Uncle Tom's Cabin. Several characters in Virginia Wolff's novels are knitters. In the first decade of the 21st century, knitting has been a key element in several novels and even murder mysteries.
Yarn for hand-knitting is usually sold as balls or skeins (hanks), although it may also be wound on spools or cones. Skeins and balls are generally sold with a yarn-band, a label that describes the yarn's weight, length, dye lot, fiber content, washing instructions, suggested needle size, likely gauge, etc. It is common practice to save the yarn band for future reference, especially if additional skeins must be purchased. Knitters generally ensure that the yarn for a project comes from a single dye lot. The dye lot specifies a group of skeins that were dyed together and thus have precisely the same color; skeins from different dye-lots, even if very similar in color, are usually slightly different and may produce a visible stripe when knitted together. If a knitter buys insufficient yarn of a single dye lot to complete a project, additional skeins of the same dye lot can sometimes be obtained from other yarn stores or online.
The thickness of the yarn is a significant factor in determining the gauge, i.e., how many stitches and rows are required to cover a given area for a given stitch pattern. Thicker yarns generally require thicker knitting needles, whereas thinner yarns may be knit with thick or thin needles. Hence, thicker yarns generally require fewer stitches, and therefore less time, to knit up a given garment. Patterns and motifs are coarser with thicker yarns; thicker yarns produce bold visual effects, whereas thinner yarns are best for refined patterns. Yarns are grouped by thickness into six categories: superfine, fine, light, medium, bulky and superbulky; quantitatively, thickness is measured by the number of wraps per inch (WPI). The related weight per unit length is usually measured in tex or dernier.
Before knitting, the knitter will typically transform a hank into a ball where the yarn emerges from the center of the ball; this making the knitting easier by preventing the yarn from becoming easily tangled. This transformation may be done by hand, or with a device known as a ballwinder. When knitting, some knitters enclose their balls in jars to keep them clean and untangled with other yarns; the free yarn passes through a small hole in the jar-lid.
There are three basic types of knitting needles (also called "knitting pins"). The first and most common type consists of two slender, straight sticks tapered to a point at one end, and with a knob at the other end to prevent stitches from slipping off. Such needles are usually 10-16 inches long but, due to the compressibility of knitted fabrics, may be used to knit pieces significantly wider. The most important property of needles is their diameter, which ranges from below 2 mm to 25 mm (roughly 1 inch). The diameter affects the size of stitches, which affects the gauge of the knitting and the elasticity of the fabric. Thus, a simple way to change gauge is to use different needles, which is the basis of uneven knitting. Although knitting needle diameter is often measured in millimeters, there are several different size systems, particularly those specific to the United States, the United Kingdom and Japan; a conversion table is given at knitting needle. Such knitting needles may be made out of any materials, but the most common materials are metals, wood, bamboo, and plastic. Different materials have different frictions and grip the yarn differently; slick needles such as metallic needles are useful for swift knitting, whereas rougher needles such as bamboo are less prone to dropping stitches. The knitting of new stitches occurs only at the tapered ends, and needles with lighted tips have been sold to allow knitters to knit in the dark.
The second type of knitting needles are straight, double-pointed knitting needles (also called "dpns"). Double-pointed needles are tapered at both ends, which allows them to be knit from either end. Dpns are typically used for circular knitting, especially smaller tube-shaped pieces such as sleeves, collars, and socks; usually one needle is active while the others hold the remaining active stitches. Dpns are somewhat shorter (typically 7 inches) and are usually sold in sets of four or five.
Cable needles are a special case of dpns, although they usually are not straight, but dimpled in the middle. Cable needles are typically very short (a few inches), and are used to hold stitches temporarily while others are being knitted. Cable patterns are made by permuting the order of stitches; although one or two stitches may be held by hand or knit out of order, cables of three or more generally require a cable needle.
The third needle type consists of circular needles, which are long, flexible double-pointed needles. The two tapered ends (typically long) are rigid and straight, allowing for easy knitting; however, the two ends are connected by a flexible strand (usually nylon) that allows the two ends to be brought together. Circular needles are typically 24-60 inches long, and are usually used singly or in pairs; again, the width of the knitted piece may be significantly longer than the length of the circular needle. Special kits are available that allow circular needles of various lengths and diameters to be made as needed; rigid ends of various diameters may be screwed into strands of various lengths. The ability to work from either end of one needle is convenient in several types of knitting, such as slip-stitch versions of double knitting. Circular needles may be used for flat or circular knitting.
It is also possible to knit using rigid frames that hold the active stitches. A new row is added by wrapping the yarn about the posts of the frame; the previous loops are pulled over the new ones, to suspend the former from the latter. The shape and number of posts of the frame can determine the type of fabric produced.
Knitting can be done in reverse using metal wire by using plaited stitches.
Various tools have been developed to make hand-knitting easier. Tools for measuring needle diameter and yarn properties have been discussed above, as well as the yarn swift, ballwinder and "yarntainers". Crochet hooks and a darning needle are often useful in binding off or in joining two knitted pieces edge-to-edge. The darning needle is used in duplicate stitch (also known as Swiss darning), while the crochet hook is also essential for repairing dropped stitches and some specialty stitches such as tufting. Other tools are used to prepare specific ornaments include the pompom tree for making pompoms conveniently. For large or complex patterns, it is sometimes difficult to keep track of which stitch should be knit in an particular way; therefore, several tools have been developed to identify the number of a particular row or stitch, including circular stitch markers, hanging markers, extra yarn and counters. A second potential difficulty is that the knitted piece will slide off the tapered end of the needles when unattended; this is prevented by "point protectors" that cap the tapered ends. Another problem is that too much knitting may lead to hand and wrist troubles; for this, special stress-relieving gloves are available. Finally, there are sundry bags and containers for holding knitting, yarns and needles.