Use decreases (dec) for shaping the necklines of sweaters, making lace patterns, and many more things. Some decreases have a definite slant either left or right; pattern instructions sometimes specify which type you should use. Left- and right-slant decreases are referred to as paired decreases.
Knit Two Together (k2tog)
The knit two together decrease is made by working into two stitches at the same time. With yarn behind your work, skip the first stitch on the left needle and insert the right needle knitwise into the second stitch and the first stitch at the same time. Knit the two stitches as if they were one stitch (fig. 17a), and remove the stitches from the left needle. This decrease leans to the right on the knit side of the work.
Purl Two Together (p2tog)
As the name suggests, this decrease is the purl-side method of the knit two together increase. With yarn in front of the work, insert the right needle through the loops of the next two stitches on the left needle as if to purl (fig. 17b); purl the two stitches as if they were one stitch, and remove the stitches from the left needle. This decrease leans to the right when viewed from the knit side.
Slip Slip Knit (ssk)
Slip slip knit is a one-stitch decrease that leans to the left and is usually paired with knit two together on knit rows.
Work this decrease as follows: Slip two stitches knitwise, one at a time, from the left needle onto the right needle; insert the left needle tip from left to right into the front loops of both slipped stitches (fig. 17c) with yarn in back. Knit both stitches together from this position.
Learn techniques for some of the other common stitches you'll find in knitting patterns, such as slip stitch, on the next page.