If you ever want to move beyond simple knit and purl you will need to add increases (and decreases) in to your work. The type of increase you use and the place you put it can create very different effects. The more you understand increases the more you can control and modify your knitting.
This is a swatch I did for a class showing different types of increases and decreases. I’ll move through different types to talk about how to work them and where they work well.
This is the most basic of increases, you just loop the yarn backwards and sit that loop on your left needle. Its easy to create but is not the tidiest looking increase. It will frequently leave a visible hole in your work.
Usually yarnovers are used in lace knitting to create a decorative hole. To work you just wrap the yarn around the needle and then work the next stitch. You can however close this hole by knitting into the back loop of the yarnover on the next row which will twist it closed. This does a surprisingly good job and creates an attractive increase. This is the increase used on the first section of the swatch above. One advantage of this increase type is that it adds extra yarn so it helps to prevent puckering of the fabric.
KNIT INTO THE FRONT AND BACK (KFB)
This is another simple increase that is fast to learn. To work it you just need to work into the front and back of the same stitch. This creates a visible ‘bar’ between the stitches which you can use as a decorative feature in places where you have increases stacked such as at raglan seams. This increase is the third sample from the bottom in the above sample.
M1L AND M1R
This is probably the increase type I use most often. It creates fairly invisible increases that have very gentle leaning to the left and the right. It is worked by picking up the bar between the stitches and knitting it. The direction you pick up and knit is dictated by the direction the increase will lean in. To lean to the right you pick up from the back and knit into the front. To lean to the left you pick up from the front and knit into the back of the stitch. You can see a complete tutorial here.
With this increase you have the potential to get some puckering when you have several increases stacked on top of each other as you are pulling up the yarn from the row below. Sometimes this increase is just listed as M1 and in that case you can pick which one you use L or R just be consistent! This is the second sample from the bottom of the swatch shown above.
LLI AND RLI
This increase pulls the side of the stitch from the row below and knits into it. For the right leaning side you pull up the right side of the next stitch and for the left leaning version you pick up the left side of the stitch just worked (one row below so it matches). This is the top increase shown in the swatch above. This increase has the the same issue as M1R/L in that it is prone to puckering due to pulling up yarn from the row below. Usually with good blocking however the effect is reduced. You can find a full tutorial for this increase here.
All of the increases I’ve discussed so far have been single increases. However several can be worked as double by just adding an extra step to the increase.
Kfbf knits into the front, back and then front again of the same stitch.
M2 knits into the front and back of the lifted bar.
WHERE TO USE THEM
Once you know what all the increases are the next step is to know where to use them! Remember that frequently you can swap in your own favourite increases in a pattern if you want to change the look. Do be aware that they may behave differently and change the way the knit will look so swatch it out before you apply it to the final piece. Any time you want to increase the width of your work you’ll work an increase, below you’ll see a few examples in garments where I use increases.