Double knitting question

Hi all…
I am brand new to this forum, just found it while I was looking online for some help with my project. I am a relatively new knitter, about 3 years, and only a few projects. But I pick up things pretty fast and have taught myself a lot with books. However, I am stuck. I am working on a sweater for my son, pattern seemed simple enough. I have just been working the back with a striped pattern, knit one row CC, purl one row CC, knit one row MC, Purl one row MC. However, I have come to a part that I am not sure what to do. I have researched, and determined it is probably double knitting, so I need to learn how to do that, but then I also have some questions. Here is what the pattern says:
[B]Keeping in pattern, k 16sts. Join second strand of yarn and bind off next 15 sts, k to end. Working both sides at once, work even in pattern until Back measures 17 inch from begining. [/B]

Ok…keeping in pattern? meaning the stripe pattern or knit one row purl next?

Join second strand of Yarn? Do I use the same color yarn? If I do, how do I double knit with the same color yarn, how do I know which yarn goes with front and which with back.

Work in even pattern? Do I knit purl now, or what does this mean. I realize I am basically doing every other sticth, but not sure which to purl and which to knit and how to figure that out.

Any help would be great! Thanks!

—Deb

You’re not doing a double knit, I think, just stripes if you’re knitting full rows with each color. You’re at the shoulders which need separate strands of yarn, because you bind off the center stitches for the neck. Keeping in pattern generally means the stitch pattern you’ve been using, though you would also continue the pattern of alternating colors. You’ll use another end of the same color you started the row with to bind off the center sts and keep knitting the other side with it. Then turn and purl back, dropping the end when you get to the bound off stitches and pick up the other end.

YOu are dividing the knitting. you have to join a second strand of the yarn as you will be knitting with two balls from this point on.

so you are knitting across the row, drop the current yarn - with a new strand of the same colour, bind off the stitches indicated and knit the remainder of the way across. turn your knitting and purl back until you reach the bound off stitches - drop the yarn you are working with. skip the bound off stitches. Using the original strand of yarn, purl across the stitches. Turn the work.

new colour, yes? knit to the bound off area, then join in a second strand of the new colour at the other side of the bound off gap, knit across, turn, etc, etc,