Darning a hole in a sock
Short answer: A hole smaller than a coin can be darned in ten minutes with a darning needle and yarn of similar weight. It lasts the rest of the sock's life.
What you need
A darning needle, yarn of roughly the same weight and colour, and something round to stretch the fabric over. An egg shape or a glass works as well as a proper darning mushroom.
How to do it
Stretch the fabric over the round object, sew a square of parallel threads across the hole, then weave threads crosswise in and out of the first ones. Finish with a few stitches around the edge. See bamboo socks for men.
When it is not worth it
If the heel is thin over a large area or the leg is slack, the sock is finished. Darning works on a hole, not on general wear. See all bamboo socks for men and bamboo socks for women.
Frequently asked questions
Can you feel a darn
A little, if it is thick. Sew flat and use fine yarn and it is barely noticeable.
How long does it last
Often the rest of the sock's life, if the hole was small when you darned it.
Can you darn with a sewing machine
Yes, many machines have a darning setting. On knitwear, hand darning often looks better.