As the name implies, you being "top-down" knitting at the neck edge and work down "in one piece" to the hem edge. This means that you don’t have to sew individual pieces together. The cut and drape of this garment are especially soft. Our summer pullover of Schachenmayr Tahiti yarn is a good first project to give this technique a try. The instructions include sizes XS – 32/24, S – 36/38, M – 40/42, and L – 44/46.