The basis of the technique is Double Knitting, and mastering it opens the door to interesting double-sided fabrics.
Sock Inside a Sock - Electronic Download.Knit them both at the same time, one inside the other. It's still a fun challenge but well within the reach of a confident sock knitter. Finished sizes:; Foot circumference: 7 1/2" (8", 8 1/2", 9", 9 1/2"); Foot length: 6 1/2" (7", 7 1/2", 8", 8 1/2"); Sizes: XS (Small, Medium, Large, XL) Designed by Katerine Atherley.