Video shows stockinette double knitting. I knit one needle on my 2-socks-in-1. Note how the left yarn (for the outer sock) always stays above the right yarn (for the inner sock)
by Nirmal creation
by Heart Hook Home
by Super Comfy
by LoomaHat.com
by Crochet Mama
by Crochet Cocoon
by Wendy Ann Lindquist