M1 & Knitting in Front and Back of the Same Stitch
There are different methods to increase stitches. M1 or "make one stitch" is one of the neatest methods because it is almost invisible. Knitting in front and back of the same stitch, though commonly used, leaves a bump in your knitting.
The following methods of increasing are shown worked on the knit side of Stockinette stitch but may also be worked on the purl side.
Knitting in Front and Back of the Same Stitch
Insert needle into the front of the stitch. Knit the stitch but do remove from left needle. (Diagram 1)
Insert right needle into back of the same stitch and knit again. (Diagram 2)
Remove the stitch from left needle. (Diagram 3)
M1 or Knitting Between Stitches
Insert left needle under thread between two stitches and knit. This will leave a small hole or eyelet. (Diagram 1)
To prevent a hole, twist the thread that you pick up between the stitches and knit. (Diagram 2)
© Reprinted with permission from Craft Yarn Council of America's Certified Instructors Program