Single Increases

A more detailed presentation can be found in this post. Here I'll sacrifice completeness and include only the techniques I deem the most useful. There is a much larger variety of increases than there are of decreases, there is also a lot more confusion with their naming. Here I'll try to use the most standard names, but, of course (and unfortunately), "standard" in knitting nomenclature is an extremely subjective term.

Before we begin

Left or right increases are called this way because of the way they look on the right-side of the work (RS). Therefore, stitches which are worked on the wrong side of the work (WS), as described below, look exactly the same as their RS counterparts. In case you're wondering, all these stitches look very similar on the WS, it's on the RS that the differences become more visible.

Another important difference between left or right increases is that they have the effect of pulling the fabric in different directions. This effect becomes very visible when increases are stacked, i.e. when the same increase is worked on every row in the same position. Increasing in alternating rows decreases this effect and above that you can neglect it, i.e. you can swap the type of increase you use without visible effect on the fabric.

In what follows I'll order the increases in terms of visibility, from more visible (and usually easier to work) to nearly invisible.

Single increases

Yarn-over increases

They create a very visible hole in the fabric and are therefore used for decorative purposes.

They are worked in the same way on the RS and WS and do not have a particular direction.

Closed-eyelet increases

They create a little hole in the fabric that, depending on the situation, can be relatively discrete. They are not very commonly used because in practice they are just a stranded increase (see below) worked in a way that creates a more visible hole.

They are worked over two rows: make a yarn-over (yo) in one row, then twist it when working it on the next row. Note that, in stranded increases the yarn-over is created in the same row it is worked (which uses less yarn and thus creates an almost invisible hole), except for that these increases are the same. The way you twist the yarn on the second row generates a right or left increase.

Left: knit or purl the yarn-over through back loop (tbl).

Right: twist the yarn-over before knitting or purling it. Note: to twist the stitch you can either, slip it knitwise (then bring it back to the left needle) or, in the first row, create an inverted yarn-over (bring the yarn over the needle from back to front).

Bar increase

This is probably the most popular increase, even though it is not very discrete. It does not create a hole, but a little bar, similar to a purl stitch, but smaller. It's popularity results mostly from its ease, but a lot of knitters find it decorative.

To work a bar increase, knit through the front and the back loops of the same stitch (kfb). On the WS, purl instead (pfb).

Contrary to what most knitters believe, the bar increase has a slant. This is only visible if these increases are stacked successively, i.e. if they're worked on every row and on top of each other. This is were things get a little complicated. So I'll make a list:

• The kfb is a left increase.
• The pfb is a right increase.
• The pfb is not the right version of the kfb. It twists the stitch below in a different way. However, for most uses, using a pfb when working a bar increase on the WS is perfectly fine.
• The kbf (knit through the back and then front loops of the same stitch), which a lot of knitters erroneously use as the mirror image of the kfb, is a left increase with the stitch below twisted differently than the kfb. Therefore, there is absolutely no reason to use this stitch.
• In the same way, the pbf (purl through the back and then front loops of the same stitch) is a right increase with the stitch below twisted differently. Therefore, there is absolutely no reason to use this stitch.
• Another variation sometimes used, namely twisting the stitch by slipping it knitwise before working it, also does not change the direction. Therefore, there is absolutely no reason to use this stitch.
• The right version of the kfb and the left version of the pfb are quite complicated to work and I won't bother to include the instructions here because I never saw them used.

Conclusion: when stacking increases, if their orientation is important, I recommend using another increase instead.

Stranded increases

These are the increases I use the most, because they offer a nice balance between ease and attractiveness. Lifted increases are more discrete, but for most uses stranded ones are good enough.

To work this increase: lift the strand between the stitches on the right and left needles and place it on the left needle, you have thus created a yarn-over, then immediately work this yarn-over as described above for Closed-eyelet increases.

Note: if you do not twist the stitch, but work it straight, you get a smaller yarn-over increase, this is called Pinhole increase, but rarely used.

Make one

The make-one increase (m1) is very often used in patterns. Different authors use it differently, but it is usually used when the kind of increase is not very important: it could be either a stranded or a lifted increase, either right or left oriented. Most often it refers to a left stranded increase (arguably the easiest to use).

Some authors also use make-one-right (m1R) and make-one-left (m1L) when the slant of the increase is important.

Lifted increases

These are the most discrete of all increases, but they do have a disadvantage: when knit on top of each other they pull the fabric unless they are worked very loosely, thus they are not recommended when working stacked increases.

Instructions:

Left: on RS, pick up stitch below the stitch just taken from needle, place it on left needle and knit it; on WS, pick up stitch below the stitch on left needle, place it on left needle and purl it.

Right: on RS, pick up stitch below the stitch on left needle, place it on left needle and knit it; on WS, pick up stitch below the stitch just taken from needle, place it on left needle and purl it.

Note: there is the question of how the stitch picked up from below is worked. Usually, this stitch is not twisted (or worked tbl). Either knitting or purling the stitch straight creates a discrete increase, twisting it makes a very tight increase which most knitters do not find as attractive.

Paired increases

Just like decreases, single increases are often used in pairs in order to create shaping, for example, in the yoke of raglan sweaters knitted top-down or in sleeves knitted bottom-up. Usually a number of stitches are put between the increases, although this is not strictly necessary. These are called guide stitches.

Paired increases are usually used in the following order:

On RS: right increase, guide stitch(es), left increase.
On WS: left-increase, guide stitch(es), right increase.

Note: in the case of increases with no particular orientation, as the yarn-over, obviously there is no particular order, but this is also the case of bar increases which are often used in pairs neglecting their orientation.