Just as the name says, this technique decreases two stitches. Simple and decorative, when done repeatedly it can create a visually emphasized and centered column of stitches.

This decrease makes one stitch out of three. It creates a decorative, slightly raised center stitch.

Slip 2 stitches together as if to knit, K1, pass slipped stitches back over last knit stitch and slip them off the needle.