Knitting one-row button holes: A simple method for creating a button hole in a knitted work. If the button you're using is 4 stitches wide, make a 3-stitch buttonhole; for a 5-st-wide button, make a 4-stitch buttonhole, & etc.
Knitting Tutorial - Matress Stitch worked horizontally to join two pieces of knitting. The stitches are in contrasting color to show detail, but I'd love to do this and add some embroidery for embellished seams on a sweater. from Knitting Daily