Darning is basically small-scale weaving. It isn’t difficult but like anything else, it takes practice but is incredible satisfying. You will need to buy a darning mushroom, although I have darned using the smaller cup from a thermos flask I would also recommend using proper darning wool if you can, although you can do a perfectly acceptable darn with double knit, it will just be a bit bulky if you’re doing a sock.
If you want to make the darn really strong, I usually just overstitch round the edges of the hole to secure ragged edges and pick up any loops of wool that could ladder. You can just do a running stich, as in the picture, but blanket stitch is stronger. Hold the fabric firmly and evenly over the darning mushroom.
2. Then, at right angles to the first lines of threads, weave the wool in and out of the rows.
3. Make sure you tie the wool off securely when you’ve finished or your hard work will be in vain.
If you’re darning a particularly large hole, for example in a jumper, I would recommend putting a piece of net across the hole and darning though that to add strength.