Ribbing is very common in hats, sweaters and anything where a stretchy fit is desired. The prequesites for knitting ribbing is a knowledge of the cast on, knit and purl stitch. Refer to previous tutorials if you want to learn more about these stitches and others. Ribbing is basically alternating the knit and purl stitch. There can be 1 by 1 ribbing, two by two, one by five or pretty much any combination. Here are some examples of ribbed projects. These are all projects made with 2 by 2 rib, in which I knit two stitches then purled two stitches, continueing in this manner until I reached the next row. On the next row, if we are kniting in the round like in the sock below, the stitches will just be a continuous knit two purl two. If the garment is knit flat, as in the case of the scarf below, the pattern that consisted of knit, knit, purl, purl... will be the opposite on the next row. A better way to think about this is to just make sure that the knit stitches line up with the purl stitches on the previous row.