After many hours of enjoyable knitting, you're finally ready to put it all the pieces together and create your jumper. Sewing the seams is the final stage in knitting a garment, and is one of the most important parts of the process. Before starting to sew, you must block the knitted pieces, or smooth out their creases and unevenness and fix their dimensions to match those on the pattern, giving an even material for sewing and ensuring a good fit. When sewing, take your time and take a break if you start to feel tired -- careful sewing up is needed for a professional finish.
Spread a towel over a flat surface, then lay a sheet over the top. Spread out the pieces of your knitted jumper over the surface, and pin the edges -- slightly stretching the material if necessary -- to match the measurements on your knitting pattern.
Spray cold water on or steam to the pieces of jumper. Check the yarn label for washing instructions. Steam machine-washable yarns. Hold the steam iron 1 or 2 cms (1/2 to 1 inch) above the fabric and move it over the whole area. Don't press down on the pieces. Alternatively, spray non-washable yarn pieces until just wet. Leave the pieces to dry completely, which may take more than 24 hours.
Thread the darning needle with contrasting colour yarn about 46 cm (18 inches) long. Sew the jumper seams together loosely, inside out. Stitch about 1 inch in from the edge, with running stitches about 1 cm (1/2 inch) long. This helps hold the seams together as you complete the final stitching.
Thread the darning needle with the same yarn used to knit the jumper. Sew the shoulder seams, armholes and arm seams before sewing the side seams. Vertical stitching on knitted fabric follows the vertical bars that run between each row of stitches. Line these up as you stitch, as if lining up strips of patterned wallpaper. Push the needle under one bar on one piece then under the corresponding bar on the other piece. Pull the thread so that it's firm but not tight. Sewing tension should be the same as the knitting tension.
Finish each length of thread by running the thread under 9 or 10 stitches on the inside of the jumper. Tie a small knot or simply cut off if the thread is hairy.
If your pieces are slightly different sizes, you can adjust for the difference by picking up two stitches on the long side for one on the short side every 2 or 3 inches, but this only works for a 1.5 cm (1/2 inch) difference. If the difference is larger you'll have to unpick and re-knit the piece that has the wrong tension according to the pattern.
Keep hands well away from the steam when using a steam iron to avoid scalding.