Ribbed hems are all well and good and they are wonderful for sweaters and other casual garments. However, what do you do if you want a hemline that does not stretch? You can knit the picot hem, https://www.instructables.com/id/How_to_knit_a_quotPicotquot_Edge/
However, this can be a bit too fancy sometimes and you might be wanting something a bit plainer with a bit more dignity. The answer is the straight edged hem.
This is a very easy hem to make.
Step 1: Beginning
I have knitted a sample to show how it is done. However, you will have to adapt it to suit whartever pattern you may be knitting.
With 3mm needles I cast on 36 stitches in gold yarn and knitted 7 rows in stockinette stitch. (One row plain and one row purl, starting with a plain row.)
Step 2: The Turn Line
After completing the 7 rows in stockinette stitch. The next row is a knit row. This will be the turn line row for the new hemline.
After knitting this row, the next row is also a knitted row.
This completes the turn section of the edge.
To continue, I have knitted 7 rows in stockinette stitch starting with a knit row.
Step 3: Continuing On
To show more clearly what the edge should look like, I changed colours to grey and knitted several more rows in that colour.
The piece that is knitted in "gold" will be your jacket (or sleeve) edge. As you can see in the photo, the old hemline (your cast on edge) desperately wants to curl up!
Your new hemline (where you see the raised knitted row) will not turn up once it is sewn neatly into place on the wrong side.
Step 4: Turn the Hem Over
Turn the knitted hemline over, wrong side to wrong side. It wants to do this naturally, and pin in place on the wrong side. Don't forget to remove the pins when you have finished sewing in place.
Step 5: Finished!
After you have sewn in place on the wrong side, and when you flip the piece over you will have a nice neat hem that will not curl up on you.