A neat hem that blends in with the rest of the knitted piece is sometimes desirable in knitting, as opposed to a ribbed or decorative edging -- as in my Classic Little T-Shirt. It makes a neat, clean edge that is in Stockinette Stitch, but the curl has been eliminated.
The knitted hem in Stockinette Stitch is quite simple, and is a useful technique to know.
Start by making a provisional cast on using a scrap of waste yarn (something smooth and slippery if possible).
Cast on the number of stitches that you require by picking up from the chain.