Slip-stitch knitting is a family of knitting techniques that uses slip stitches to make multiple fabrics simultaneously, to make extra-long stitches, and/or to carry over colors from an earlier row. Basic methods In the basic slip stitch the stitch is passed from the left needle to the right needle without being knitted. The yarn may be passed invisibly behind the slipped stitch (wyib="with yarn in back") or in front of the slipped stitch (wyif="with yarn in front"), where it produces a small horizontal "bar". The wyif slipped stitch is less common, although several knitting patterns use it to produce a visual effect like woven cloth. Alternatively, the yarn can be "tucked", i.e., made into a yarn-over that is knitted together with the slipped stitch on the next row; like the simpler wyib, this is invisible. If knitted on the next row, the wyib slipped stitch is twice as tall as its neighboring stitches. A vertical column of such "double-height" stitches is a nice accent, e.g., on a scarf or in a sweater, particularly in a contrasting color. Double knitting with slip stitches Slip stitches may be used for an easier method of double knitting that requires only one yarn be handled at one time. As a concrete example, consider a two-color pattern with a multiple of four stitches (labeled ABCD) being knit on double-pointed circular needles. On the first row, using color 1, stitch A is knitted, stitch B is purled, stitch C is slipped wyib and stitch D is slipped wyif. The knitter then slides the stitches back to the beginning (recall that the needles are double-pointed). Then, using color 2, stitch A is slipped wyib, stitch B is slipped wyif, stitch C is knitted and stitch D is purled. The knitter then turns the work and repeats indefinitely. The knitted and slipped wyib stitches come forward, whereas the purled and wyif stitches recede, resulting in a (very warm!) double-knit scarf alternating in the two colors with beautiful drape. The knit and purl stitches produce the front and back fabrics, respectively, of the double-knitted fabric while the slipped stitches allow for the alternation of color. An even simpler slip-stitch pattern generates two fabrics at once on the same needle. Consider the pattern: * knit 1, slip 1 wyif *. At the end of the row, turn the work. Then knit the stitches that were slipped and slip (again wyif)