Things You'll Need
Beginning knitters often start out making long strips. Many of these strips become scarves, but they can also turn into something more interesting. All it takes to transform your knitted strips into blankets or afghans is a technique called the mattress stitch. When used for sewing together strips of stockinette, the fabric created by alternating knit and purl rows, mattress stitch creates an almost invisible seam. Because you sew mattress stitch by hand, it can be time-consuming, but the end result is a clean and even seam.
Thread a darning needle with a piece of yarn that is at least twice as long as the knitted strips you want to sew together. Insert only the last two to three inches of the yarn through the eye of the needle. Do not double it over or knot it as you would with regular sewing thread.
Tie the end of the yarn that is farthest from the needle to the cast-on or bind-off tail of one of the two knitted strips. A square knot works best. Lay the strips, so that the tied ends are at the bottom of the work and the right-sides are facing up.
Locate the second vertical row of stitches from the edge of the strip on the right. In stockinette stitch, this will look like a column of Vs.
Insert the needle under both legs of the V, closest to the bottom of the column.
Pull the yarn across to the knitted strip on the left. Insert the needle under both legs of the corresponding V on that side. Pull the yarn all the way through, so that the V on the right and the V on the left are side-by-side, and the edges of the strips turn under.
Insert the needle under both legs of the next V, up on the left. Pull the yarn across and sew through the next V up on the right.
Continue sewing up the row in this fashion, working from right to left and left to right, until the strips are joined.
Tie the yarn in a knot at the top of the row and remove the darning needle from your work.