Seaming adds a multitude of benefits to your knitting - it provides structure at important locations on a garment, such as the side seams and armhole. Knitting garments in pieces and then seaming also enables you to do modifications on individual pieces rather than the whole garment at once.
I could go on, but the fact that a lot of our garment patterns all utilize seaming in some way is a pretty good indication of how we feel about it.
NOTE: My pieces (the Amanda Cardigan) are knit in a slubby 2-ply, so I’m seaming with a fine gauge smooth 3-ply in a similar color.
STEP 1 / Place the darning needle from front to back in the open space between the 1st and 2nd stitch on the first row of your knitting. I like to start on the piece that will sit on the right.
STEP 2 / Bring the needle up to the front in the second row of your knitting. Make sure to stay along the same column of stitches (in between the 1st and 2nd stitch from the edge). Pull your working yarn thorough, leaving a 4” tail for weaving in.
STEP 3 / Repeat steps 1 + 2 on the left piece that you are seaming. Pull the needle and yarn through, but do not pull too tightly - you should have about 3/4" - 1" space between the pieces.
STEP 4 / Place your darning needle into the right piece in the space that you came out of in Step 1. Bring the needle up to the front in the next row of your knitting.
STEP 5 / Repeat Step 4 in the left piece of knitting, making sure to not pull the seaming yarn too tightly.
STEP 6 / Repeat steps 4 + 5 until you have worked about 1” of your knitting. Make sure to go into the same space that you worked previously, so you move up a full row after working each step two times.
STEP 7 / Holding both the tail and your working yarn, slowly pull the seaming yarn tight. Once complete, your seam should lay flat and not buckle and your seam yarn should not be visible.
STEP 8 / Repeat steps 4 + 5 for another inch of your knitting. Pull the working yarn taut. Continue in this manner, stitch back and forth for about an inch, then pulling tight, until you reach the end of your work.
STEP 9 / Holding the bottom edge, pull the seaming yarn up so the two pieces close.
STEP 10 / Continue in this manner, working back and forth for about an inch, then pulling tight, until you reach the end of your work. Since I have the exact same number of rows on each piece and I’m working evenly up the work, I will end with my top seam perfectly aligned.
Once complete, the seam should look neat on both inside and out. The knitted fabric should lay flat and not buckle or curl. You may weave in the seaming ends now, or continue on with the armhole if applicable.