A SK2P is a left-leaning, double decrease, where you slip one stitch, k2tog, and then pass the slipped stitches over the k2tog. This decrease turns three stitches into one (decreasing two). One stitch is decreased in the k2tog and one by passing the slip stitch over. It is similar to the S2KP, slip two stitches, knit one stitch, and then pass the slipped stitches over the knit stitch. By “centered double decrease” I mean that this is a decrease that turns three stitches into one (decreasing two), and also does not lean to the left or right.
Working an SK2P
Slip 1 stitch as if to purl, then k2tog in the next two stitches, finally pass the slip stitch over the stitch created by the k2tog and off the right needle.
Working an SK3P – a variation on SK2P
Slip 1 stitch as to purl, k3tog, then going into slipped stitch from left to right, use the left needle tip to pass the slipped stitch over the k3tog and off the right needle.
To pass the slip stitch over
Use the tip of the left needle to pass the slipped stitch over the k2tog (or k3tog) and off the right needle.