Once I had my sleeves (and body) all knitted up, it was time to join the whole thing together. On first glance, this seems like it would be difficult to do, cumbersome and fiddly, but it’s not too tricky, actually. Just go slow, and make sure you count your stitches correctly!
The goal is to end up with the sleeves arranged on either side of the body, with active stitches all the way around (so that you can keep knitting the shoulders). If you are imagining looking at your sweater from the top down, it would look something like this:
Start knitting at the beginning of your round (usually the center back of a pullover, or the center front for a cardigan). Make sure to use a great big circular needle, or you’ll run into trouble in a few minutes! Work your way across the body of the sweater until you reach the armpit.
Then, pick up your sleeve and knit around the outside of the sleeve, leaving its armpit unworked. Leave the active armpit stitches on a piece of scrap yarn or a stitch holder.
Switch back to knitting the body, and work your way all the way across the back (or front) of your sweater.
Then, repeat the process for the other sleeve, knitting around the outside of the sleeve, while leaving the armpit alone.
The final step is to close up the armpits. Attach the sleeve armpit stitches to the body armpit stitches on either side. I like to use the Kitchener stitch, but you could also use a 3-needle bind-off, if that’s your favorite.
Now you’re all set up for the knitting the shoulders on your bottom-up sweater! Just keep going in the round (if you’re making a pullover), or turn the work and go back the other direction (if you’re making a cardigan). Simple!