By working stitches through the back loops only, you come up with a taut, stable fabric. The gauge becomes slightly smaller due to the consistent twisting of the stitches. It is worthwhile to note that this pattern will list slightly to the left. This can be remedied somewhat by blocking the finished work.
Instructions (flat knitting)
Row 1: Knit all stitches through back loop
Row 2: Purl all stitches through back loop
Repeat these two rows
Instructions (knitting in the round)
Round 1: Knit all stitches through back loop
Repeat this round