How to Seam 2 finished knitted pieces with a knit strip

How to seam two finished pieces of knitting with a knitted section, this technique can be particularly useful if you are making a blanket with many squares, or have made a garment that needs a little extra room. This seaming is easily removed as all you have to do is rip it out the same way you would with any knit fabric, and could be used for a design purpose such as adding a stripe of alternating color or a decorative element like a cable. 

To begin gather your two pieces that need joining a set of needles ( or just 2 dpns) and the yarn you want to use. For the first section of this tutorial I am working on joining up two separate samples, the green one will end up on the right hand side of the join and the white one will end up on the left hand side of the join. Cast on stitches using the backwards loop method, for these samples I cast on between 5 and 7 stitches. 

To work the backwards loop method hold the yarn in your left hand with the active tail coming from the back of your thumb around to the front in a counterclockwise manner. Bring the needle under the loop in front of the thumb and drop your thumb out, tension stitch and repeat.  I chose this method for cast on because it does not leave a chunky edge cast on and so sits more flush with the edge of the fabric. 

Now turn the work and knit to the last stitch, slip this stitch knitwise changing the slant of the stitch.

This will be a little fiddly since this is simply a twisted loop on the needle but it will work out I promise. Now look for your first pickup spot  on the work, this first pickup will be worked on the left hand side of the piece as you are looking at it. For this join the green piece is on the right side and the white piece is on the left side so we are picking up from the white piece first. Your first pickup spot will be the 2nd row in from the edge, these swatches both have a garter stitch edge so there will be one pickup in between each garter ridge. 

Pickup and Knit 1 stitch into this spot, now without changing the stitch slant the left needle tip needs to be inserted into the front loops as shown. 

This can either be achieved by slipping both stitches back to the left tip and inserting the right tip through the back loop, or simply inserting the left tip from back to front through the front loops. Wrap yarn and pull through, this is working a k2tog through the back loops.

Entire Row 1 is as follows (RS): K to last stitch, slip 1 kwise, pickup and knit 1 stitch into edge of work, insert left needle tip from back to front through front loops, K2tog tbl. 

Now turn the work, slip the first stitch purlwise, purl across to the last stitch, slip this stitch purlwise tip to tip which does not change the slant of the stitch. Now here is the tricky part, keeping the yarn forward and working from back to front insert the needle into the swatch. This means that the needle has to come from the rightside of the the work to the wrongside of the work, which is challenging because the wrongside is facing at the moment. 

First picture you can see that the yarn is in front of the work, then you bring the needle from back to front and then pull up a stitch. Now you need the left tip inserted into these stitches in the back, so either slip both stitches to the left needle tip to tip and insert the right needle to work a p2tog, or just insert the left needle tip into the back from left to right. Wrap and pull through as a p2tog, you can see that the work is now joined with 2 rows of stitches.

Entire Row 2 (WS): Slip 1 pwise, p to last stitch, sl1 pwise, with yarn in front of work and wrong side of work facing pickup and purl 1 stitch from back to front, slip both stitches to left needle and p2tog. 

Row 3 (RS): Sl1 pwise, K to last stitch, slip 1 kwise, pickup and knit 1 stitch into edge of work, insert left needle tip from back to front through front loops, K2tog tbl. 

Now work Row 3 for the next right side ( it begins with a slipped stitch, that's the only difference) and repeat Rows 2-3 for the remainder of the join, make sure to pick up 1 stitch for every 2 rows, so either 1 in each garter valley or every second 'V' on your edge. This is the location of the second pickup, on the other side of the garter bump. 

And the location of the next wrong side row pickup, again a garter bump away from the first one. 

Here is the finished piece, as you can see the join is fairly invisible on the cream colored side but more obvious with the contrast color, something to keep in mind. If you want to use a contrast color and have less show at the join try using a thicker yarn with smaller needles. 

Just for fun I altered the join halfway through to show what it would look like if the rows were actually written as this:

Row 1 (RS):  K to last stitch, slip 1 kwise, pickup and knit 1 stitch into edge of work, pass slipped stitch over, turn work

Row 2 (WS): P to last stitch, sl1 pwise, with yarn in front of work and wrong side of work facing pickup and purl 1 stitch from back to front, pass slipped stitch over, turn work

This changes the join slightly but creates a more looped decorative edge, I bet you could pick up into those loops pretty nicely and work some lace, or another cable or, or, or...

And here is the same basic technique worked on a sample sleeve, if you knit a sweater and find you need more room in circumference of the sleeves and body you could join it with an inch of work at each seam and have a better fit!