These instructions are from http://knitting.about.com/od/stitchg...g/slip_rib.htm
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Slip Stitch Rib
Works on odd numbers of stitches.
Knit one, *slip one with the yarn in front, knit one. Repeat from * to end.
Repeat these two rows for pattern.
Note: Slipping the stitch with the yarn in front means you move the yarn from the back to the front, as if to purl, then slip the stitch as if to purl, move the yarn back to the back of the work and knit the next stitch.
This makes a horizontal bar on the right side of the fabric, which adds an interesting texture to an otherwise basic rib.