Slip, Slip, Slip, Purl (sssp)

The sssp, or slip-slip-slip-purl, is a left-leaning double decrease. It takes three stitches and turns them into a single stitch that slants toward the left on the right side of the work. It is generally worked on the wrong side and looks like a slip, slip, slip, knit (sssk) on the front.

To work a sssp, slip the first stitch on the left-hand needle as if to knit, then slip the second stitch on the left-hand needle as if to knit, then slip the third stitch on the left-hand needle as if to knit. Slip these three stitches back onto the left-hand needle, preserving the twist you've just added. Finally, purl these three stitches together through the back loop.

The following video demonstrates how to work a sssp: