This tutorial shows how to increase the number of stitches by two (make 2 additional stitches out of one stitch). This may be shown as the abbreviation inc 2, or as kfbf “knit into the front and back and front of the stitch”.
If your pattern tells you how to work a double increase, then do follow those instructions, But if not, here is how I work a double increase.
What is a double increase?
For a double increase you will make an additional 2 stitches.
For example, if you started with 10 stitches and the pattern states:
knit 9, inc 2 (12 sts)
You would knit 9, then on the last stitch you would work a double increase. This makes 2 extra stitches for 12 stitches in total (10 plus 2).
Compare this with the kfb increase which only increases by one stitch. Here the instruction would be:
knit 9, kfb (11 sts)
You would knit 9, then on the last stitch you would work a kfb increase. This makes 1 additional stitch for 11 stitches in total (10 plus 1).
How to inc2
Step 1: Knit to the point of the increase. Knit into the front of the next stitch but do not let it fall off the needle
Step 2: Then knit into the back of the same stitch, but again, do not let it fall off the needle. So far, this is just the same as KFB except we have kept the stitches on the needle.
Step 3: Knit into the front of the same stitch again. You have now made two additional stitches (three stitches have been made out of one).
On this little sample of stockinette stitch, I have cast on 3 stitches and made an increase on the middle stitch of every knit row so you can see how the knitting slopes on either side of the knitting.