Here is one thing I know that is actually useful. As top tips go, it gets high marks for quaintness, as the repairing of things now seems fusty and peculiar in a time marked by rapid obsolescence and easy expendability. The mending of socks is what your grandmother did, certainly what my grandmother did, aided by that proper mending tool, the darning ball, a device crucial to the business of sock mending and richly burnished from frequent use. For this repair, neither a darning ball nor a darning needle is necessary.
What You Need:
A well-worn sock, incomplete with hole; a felting needle; some fleece or roving.
You can insert a small piece of rubber foam into the sock, but I have found it easier to stretch the sock across an empty glass, or, in this case, an empty espresso can.
How It Works:
Take a piece of roving or fleece and pull it apart to separate the fibers. Place the fibers over the hole in the sock. Repeatedly punch the felting needle into the fleece; the fibers from the sock and fleece will knit together, creating a patch of felt. No doubt, you will be more conscientious than I and use a color of fleece or roving that matches your sock elegantly and cannot be detected by any but the most obsessive.
Wash your sock by hand or in the machine. The soap and agitation will continue to felt the fleece and your sock will be whole again. You may want to needle-felt the patch further to tack down any stray fibers. Perhaps this is a strategy that may be less successful with cashmere, but for an otherwise hardy hiking sock, it works wonderfully.
Alas, I cannot claim credit for this clever idea; that honor must go to an acquaintance with whom I have lost touch, but who I remember with gratitude.