I have just tried an idea out on a swatch:
if you want to prevent the side of st st from curling, you can do a side "hem edge". I knit this as "knitting in the round on straight needles" for 5 stitches or so.
Does this have a name? I haven't seen this before but I do not want to claim that I did invent something new. Most likely it has been done
I want to use it for cardigans, for example, where an edge of the knitting will show and be exposed.