Hey. I'm going to show you how to sew up the seam from the cast-on edge and the cast-off edge of an item, such as these garter stitch mitts. I'll be showing how to sew this seam here, and this seam here.
I've got it started here for you. I have loaded the tail onto a tapestry needle with a blunt tip. Basically what I'm going to be doing is I'm going to be coming under 2 pieces of yarn. There's 1, there's 2; I'm going to stick the needle under there. I'm going to pull not too tightly because I want to try to replicate with the sewing yarn the same tension that I was getting with my knitting needles.
I'm going to come back under the side that's closer to me, under 2 pieces of yarn. I'm going to pull tight, but not too tightly. If you leave it too loose, you'll be able to see your skin between the 2 edges. If you leave it too tight, it's going to be stiff and immobile, and feel strange. I'm coming underneath every time, so from the inside of the mitten out, catching 2. Like a shoelace, zigzagging under, catching 2 from this side, catching 2 from this side. Every once in a while, just giving it a little test stretch, just to make sure that I'm getting the tension right. Coming under 2.
The reason why we want to come under 2 pieces of yarn instead of 1 is because if we come under just one piece yarn of yarn, because knitting is a loop, it's going to pull the other part of the loop out of alignment, and you're going to get this big, gaping hole. We don't want any holes in our sewing seams. We're going to go instead under 2 pieces of yarn, and that renders a much quicker seam.
When I've gone as far as I need to go, I'm going to reverse the process to tuck in the end and make this a really strong stop. I just came out of this side; I've been zigzagging and shoelacing all the way up. What I'm going to do is I'm going to duck under from the top this time, and come out. Before I pull that loop really right, I'm going to stick my needle down into it, and pull, so that I've made a little . . . it's a knot, but it's just a little hitch.
What I'm going to do is I'm going to stick my needle into the inside of the fabric, and I'm going to flip it inside-out and weave that end under a piece of yarn from the top, and then from the bottom, and the top. This is just hiding my end, so that if anything were to happen to the top of that seam, the end wouldn't be right there ready to unravel. There's no way that this is going to unravel.
Now that I've woven it in an inch or so from the site of the reversal, it's safe for me to trim close to the surface of the knitting. That's sewing the seam. Coming up to where I want it to, stop, reversing it, tucking it into that little half-hitch, and then hiding the seam on the inside. Then I would do the same thing. I would use one of these tails up here, going from underneath 2 to underneath 2, all the way down to where I wanted it to stop on this side. Reversing it with that half-hitch, and weaving in the ends. Then you get this nice seam that is flexible, feels like part of your knitting, and holds your ends securely in place. Good luck with your mitts.