I’ve discovered mattress stitch, or as June Hemmons Hiatt (in the enormous brick that is The Principles of Knitting) has it, running thread seam. The main annoying thing about that book is that she refuses to use common parlance, in favour of renaming almost everything. What is worse, is that the index then becomes less than helpful, other than as a general direction to the relevant chapter.
Anyway, I’ve discovered mattress stitch. I may be some time. Despite the main body of my son’s birthday sweater being knit in one piece, there are a lot of seams to sew.