By no means an expert, but My mother showed me how when I was about 8. Mum would break out the knitting needles and knit a new heel or toe. This is on the heavy wool boot socks, that I wore at the shipyard. My current boot socks are Thinsulate, 3 pieces stitched togetther. Git 'em from LL Bean The stitching lets go , so I fix them . I normally wear cotton socks now- a-days. I buy them by the 6 pack and dispose of worn socks as they appear.